皮質(zhì)醇日常節(jié)律與兒童問題行為及心理社會(huì)因素的關(guān)系*

聶瑞虹 許 穎 韓 卓

(1北京師范大學(xué)心理學(xué)院應(yīng)用實(shí)驗(yàn)心理北京市重點(diǎn)實(shí)驗(yàn)室, 北京 100875)(2泉州幼兒師范高等?？茖W(xué)校, 福建泉州 362000)

HPA軸是神經(jīng)內(nèi)分泌系統(tǒng)的重要組成部分,可以調(diào)節(jié)日常激素分泌的節(jié)律性。其在個(gè)體面對(duì)壓力源時(shí), 可以通過一系列的途徑使激素水平升高, 從而使人體產(chǎn)生應(yīng)激反應(yīng)。因此, HPA軸對(duì)個(gè)體情緒調(diào)節(jié)、行為控制等過程具有重要作用。皮質(zhì)醇作為HPA軸的終產(chǎn)物, 表現(xiàn)出一定的晝夜節(jié)律變化。其中, 唾液皮質(zhì)醇因其收集的簡(jiǎn)便性、非侵入性, 成為目前應(yīng)激研究中最為常用的 HPA軸活動(dòng)指標(biāo)。皮質(zhì)醇的水平在每天清晨起床后30分鐘內(nèi)急劇升高, 并在起床后 30～45分鐘左右達(dá)到最高值(Wilhelm, Born, Kudielka, Schlotz, ＆amp;Wüst, 2007), 隨后在一天內(nèi)逐漸下降, 直到睡覺前達(dá)到最低值(Schmidt-Reinwald et al., 1999)。目前, 研究多采用日常皮質(zhì)醇斜率變化、皮質(zhì)醇覺醒反應(yīng)和皮質(zhì)醇分泌量來評(píng)估HPA軸的活動(dòng)。其中, 皮質(zhì)醇斜率變化(Diurnal cortisol slope)指皮質(zhì)醇濃度從早到晚的下降速率。元分析發(fā)現(xiàn), 平緩的斜率往往伴隨著較低的早晨皮質(zhì)醇水平和較高的晚間皮質(zhì)醇, 與慢性壓力有關(guān) (Miller, Chen, ＆amp;Zhou, 2007)。皮質(zhì)醇覺醒反應(yīng)(cortisol-awakening response, CAR)是指依據(jù)個(gè)體早晨覺醒時(shí)間, 皮質(zhì)醇水平在醒后 1個(gè)小時(shí)內(nèi)表現(xiàn)出急劇的增加, 達(dá)到峰值后開始降低并在醒后1個(gè)小時(shí)左右回到基線水平。而皮質(zhì)醇分泌量(total cortisol output/area under the curve, AUC)指一段時(shí)間內(nèi)皮質(zhì)醇分泌的總量。

盡管有研究通過測(cè)量皮質(zhì)醇的應(yīng)激反應(yīng)評(píng)估個(gè)體的健康水平, 但應(yīng)激反應(yīng)的測(cè)量仍然存在一定缺陷。與之相比, 皮質(zhì)醇的日常節(jié)律的測(cè)量則表現(xiàn)出了一定的優(yōu)越性。首先, 雖然部分研究試圖通過實(shí)驗(yàn)任務(wù)測(cè)量應(yīng)激條件下個(gè)體的皮質(zhì)醇反應(yīng), 但實(shí)驗(yàn)室任務(wù)可能與實(shí)際生活中的壓力存在一定差異, 因此很難推斷出日常情況下HPA軸的壓力反應(yīng)機(jī)能。其次, 環(huán)境因素對(duì)生理的影響往往是慢性的、長(zhǎng)期的, 通過逐步改變機(jī)體的穩(wěn)態(tài)對(duì)身體健康造成影響。而實(shí)驗(yàn)室的應(yīng)激壓力只能模擬一個(gè)有限的壓力過程, 即使能夠發(fā)現(xiàn)應(yīng)激條件下皮質(zhì)醇的活動(dòng)模式, 也無法提供日常條件下皮質(zhì)醇的活動(dòng)情景(Saxbe, 2008)。第三, 研究發(fā)現(xiàn)日常條件下皮質(zhì)醇的活動(dòng)與個(gè)體的生理、心理健康聯(lián)結(jié)更為緊密(Sapolsky, Romero, ＆amp; Munck,2000)。因此, 本文主要關(guān)注相對(duì)穩(wěn)定的皮質(zhì)醇日常節(jié)律的研究。

個(gè)體每日皮質(zhì)醇分泌總量相對(duì)于正常值的顯著偏高或偏低、每日變化趨勢(shì)過于平緩等都被視為皮質(zhì)醇水平失調(diào), 而這種失調(diào)可能對(duì)個(gè)體身體健康、行為問題、認(rèn)知能力和情緒調(diào)節(jié)能力等產(chǎn)生影響(Blair, Granger et al., 2011; Chrousos, 2009;Fries, Hesse, Hellhammer, ＆amp; Hellhammer, 2005;Lopez-Duran, Kovacs, ＆amp; George, 2009; Sapolsky,Romero, ＆amp; Munck, 2000; Zalewski et al., 2012)。研究表明, 較低的皮質(zhì)醇水平往往預(yù)示著HPA軸的損傷(Heim, Ehlert, ＆amp; Hellhammer, 2000; Gunnar ＆amp;Vazquez, 2001), 而較高的皮質(zhì)醇水平會(huì)損害記憶和警覺等認(rèn)知能力, 并與抑郁和焦慮等癥狀相關(guān)(Lupien, Maheu, Tu, Fiocco, ＆amp; Schramek, 2007;Plotsky, Owens, ＆amp; Nemeroff, 1998)。

目前, 研究發(fā)現(xiàn)皮質(zhì)醇的日常分泌活動(dòng)與個(gè)體的行為問題有關(guān), 且受到早期環(huán)境的影響(Cicchetti,Rogosch, Gunnar, ＆amp; Toth, 2010; Holsboer, 2000)。例如, 5歲前受到軀體虐待和性虐待的7～13歲兒童更容易出現(xiàn)HPA軸皮質(zhì)醇日常斜率減緩的情況(Cicchetti et al., 2010)。而對(duì)于臨床抑郁的成年人研究也發(fā)現(xiàn)了神經(jīng)內(nèi)分泌系統(tǒng)失調(diào)狀況(Holsboer,2000)。成人神經(jīng)分泌系統(tǒng)已發(fā)展穩(wěn)定, 而對(duì)兒童而言, 其神經(jīng)內(nèi)分泌系統(tǒng)正處于迅速發(fā)展階段。促腎上腺皮質(zhì)激素釋放激素和皮質(zhì)醇不但對(duì)于大腦發(fā)育起到關(guān)鍵作用, 同時(shí)會(huì)影響神經(jīng)營(yíng)養(yǎng)因子并調(diào)控基因的轉(zhuǎn)錄(Gunnar ＆amp; Vazquez, 2006)。因此, 皮質(zhì)醇的日常節(jié)律與兒童的內(nèi)外化問題行為值得關(guān)注。且根據(jù)以往研究, 皮質(zhì)醇日常節(jié)律常受到兒童生活的環(huán)境及早期經(jīng)歷, 諸如家庭社會(huì)經(jīng)濟(jì)地位、受照顧情況等心理社會(huì)因素的影響。因此, 本文旨在梳理國(guó)內(nèi)外文獻(xiàn)中關(guān)于兒童皮質(zhì)醇日常節(jié)律的研究, 尋找皮質(zhì)醇與兒童問題行為關(guān)系的規(guī)律性, 并通過皮質(zhì)醇水平的變化探尋影響兒童發(fā)展的危險(xiǎn)性因素和逆境環(huán)境中有利于兒童成長(zhǎng)的保護(hù)性因素, 試圖發(fā)現(xiàn)環(huán)境對(duì)兒童行為影響的神經(jīng)內(nèi)分泌機(jī)制。同時(shí), 對(duì)未來的研究方向進(jìn)行展望。

1 皮質(zhì)醇與兒童問題行為

皮質(zhì)醇的日常節(jié)律失調(diào)往往與兒童的問題行為有關(guān)。其中, 問題行為是指?jìng)€(gè)體表現(xiàn)出的妨礙其社會(huì)適應(yīng)的異常行為(林崇德, 楊治良, 黃希庭,2003), 通?？煞譃閮?nèi)化問題行為(Internalizing Problems)和外化問題行為(Externalizing Problems)兩大類(Achenbach, 1991)。內(nèi)化問題行為是指兒童青少年經(jīng)歷的一些不愉快或消極的情緒, 包括抑郁、焦慮、退縮、低自尊等; 而外化問題行為則主要是指違反道德和社會(huì)行為規(guī)范的行為, 包括攻擊、反抗、盜竊、逃學(xué)等。目前, 西方研究多集中于探討皮質(zhì)醇活動(dòng)與兒童問題行為的關(guān)系, 并通過進(jìn)一步觀察探討環(huán)境因素對(duì)兒童行為的生理機(jī)制。

1.1 皮質(zhì)醇與內(nèi)化問題行為

目前, 關(guān)于皮質(zhì)醇水平與內(nèi)化問題行為的關(guān)系的研究并沒有得到一致的結(jié)論(Dockray et al.,2009; Goodyer et al., 1996) (見表1)。這些研究主要分為橫斷研究與縱向追蹤研究。其中, 橫斷研究指的是是對(duì)某一個(gè)特定點(diǎn)上的幾個(gè)不同組(通常是具有不同的年齡)之間的比較, 縱向追蹤研究指的是指在一段相對(duì)長(zhǎng)的時(shí)間內(nèi)對(duì)同一個(gè)或同一批被試進(jìn)行重復(fù)的研究。多數(shù)橫斷研究發(fā)現(xiàn), 較高的皮質(zhì)醇基線水平與內(nèi)化問題行為有關(guān)(Cicchetti ＆amp; Rogosh, 2001; Claes, 2004; Osika,Friberg, ＆amp; Wahrborg, 2007; Pérez-Edgar, Schmidt,Henderson, Schulkin, ＆amp; Fox, 2008; Vigil, Geary,Granger, ＆amp; Flinn, 2010), 但也有橫斷研究得出了相反的結(jié)論(De Bellis et al., 1996; Granger, 1998)。此外, 還有研究發(fā)現(xiàn), 環(huán)境因素也會(huì)對(duì)皮質(zhì)醇與內(nèi)化問題行為的關(guān)系造成影響。例如, 抑郁的受虐待兒童與非抑郁的受虐待兒童相比日常皮質(zhì)醇節(jié)律更平緩(Kaufman, 1991)?？梢? 有關(guān)皮質(zhì)醇日常節(jié)律的橫斷研究不盡相同。而有關(guān)皮質(zhì)醇日常節(jié)律的縱向研究結(jié)果則較為一致, 即皮質(zhì)醇基線水平與內(nèi)化問題行為正相關(guān)(Greaves-Lord et al.,2007; Lopez-Duran et al., 2009)。多數(shù)青少年研究表明, 較高的皮質(zhì)醇基線水平往往與后期抑郁癥狀有關(guān)(Goodyer, Park, ＆amp; Herbert, 2001; Halligan,Herbert, Goodyer, ＆amp; Murray, 2007)。Smider 等(2002)也發(fā)現(xiàn), 正常兒童學(xué)齡前較高的皮質(zhì)醇可以預(yù)測(cè)學(xué)齡期的內(nèi)化問題行為。

皮質(zhì)醇水平與兒童內(nèi)化問題研究之所以存在差異, 主要取決于研究類型是橫斷研究還是縱向研究(Shirtcliff ＆amp; Essex, 2008)。Ruttle等人(2011)同時(shí)進(jìn)行橫斷研究和縱向研究后發(fā)現(xiàn)：橫斷研究中, 兒童期高水平的皮質(zhì)醇基線與內(nèi)化問題行為負(fù)相關(guān), 而縱向研究卻發(fā)現(xiàn)童年較高的基礎(chǔ)皮質(zhì)醇可以預(yù)測(cè)青少年期更多的內(nèi)化問題行為。為了解釋研究類型對(duì)皮質(zhì)醇與兒童內(nèi)化問題行為的影響, Miller等人(2007)對(duì)于 107項(xiàng)研究進(jìn)行元分析。結(jié)果發(fā)現(xiàn), 雖然最初橫斷研究結(jié)果并不一致,但是如果將研究按照兒童暴露在壓力中的時(shí)間長(zhǎng)短進(jìn)行分類, 則可發(fā)現(xiàn)童年早期已經(jīng)處在壓力條件下的個(gè)體更可能表現(xiàn)出較低的皮質(zhì)醇水平。他們認(rèn)為, 壓力暴露最初可能導(dǎo)致HPA軸活動(dòng)上升,但慢性壓力則會(huì)導(dǎo)致HPA軸活動(dòng)失調(diào), 皮質(zhì)醇分泌降低, 活動(dòng)減緩。根據(jù)適應(yīng)負(fù)荷理論, 當(dāng)壓力持續(xù)存在時(shí), 壓力系統(tǒng)(包括 HPA 軸和交感腎上腺系統(tǒng))會(huì)處在一個(gè)較高的適應(yīng)負(fù)荷之下, 為了適應(yīng)這種壓力, 系統(tǒng)會(huì)升高基礎(chǔ)水平, 改變之前的穩(wěn)態(tài)。而壓力系統(tǒng)長(zhǎng)期超負(fù)荷工作會(huì)使HPA軸的調(diào)節(jié)作用的靈活性降低, 這就解釋了為什么橫斷研究與縱向研究的存在差異。此外, 因?yàn)槟行院团越?jīng)常經(jīng)歷不同的情緒, 所以被試的性別也可能會(huì)對(duì)研究結(jié)果產(chǎn)生影響。如一項(xiàng)針對(duì)10歲以上的兒童的研究發(fā)現(xiàn), 女生中情緒問題與皮質(zhì)醇水平正相關(guān)(Osika et al., 2007), 而男生中皮質(zhì)醇與悲痛正相關(guān)(Vigil et al., 2010)。

表1 兒童皮質(zhì)醇日常節(jié)律與內(nèi)化問題行為的關(guān)系研究

1.2 皮質(zhì)醇與外化問題行為

盡管皮質(zhì)醇與內(nèi)化問題關(guān)系的研究結(jié)論存在差異, 但與外化問題之間關(guān)系的研究結(jié)論卻較為一致。二者的關(guān)系與不同的皮質(zhì)醇指標(biāo)、兒童的年齡及性別有關(guān), 且受到不同皮質(zhì)醇測(cè)量方式的影響(見表2)。采用日常皮質(zhì)醇節(jié)律測(cè)量的研究表明, 兒童期平緩的日常皮質(zhì)醇節(jié)律、較低的皮質(zhì)醇基線和較高的晚間皮質(zhì)醇往往能預(yù)測(cè)較為嚴(yán)重的外化問題行為(Poustka et al., 2010; Shirtcliff ＆amp;Essex, 2008; Shoal, Giancola, ＆amp; Kirillova, 2003;Marsman et al., 2008; Sondeijker et al., 2007)。為了探究年齡對(duì)皮質(zhì)醇與兒童外化問題行為的影響,Alink等人(2008)對(duì) 72項(xiàng)研究進(jìn)行了元分析的結(jié)果發(fā)現(xiàn), 學(xué)齡前期兒童(3～6、7歲)的外化問題行為與較高的皮質(zhì)醇基線水平有關(guān); 學(xué)齡期兒童(6、7～12歲)的外化問題行為與較低的皮質(zhì)醇基線水平有關(guān); 而青少年(12～18歲)中皮質(zhì)醇與外化問題行為無顯著相關(guān)。此外, 學(xué)齡前兒童高基線皮質(zhì)醇與高外化問題行為的關(guān)系還可能受到早期生活壓力、甚至出生前環(huán)境的影響(Gunnar ＆amp; Cheatham,2003; McBurnett, Lahey, Rathouz, ＆amp; Loeber, 2000)。與學(xué)齡前期兒童相反, 學(xué)齡期兒童外化行為和皮質(zhì)醇基線水平的負(fù)相關(guān)。為了解釋低皮質(zhì)醇基線水平與高外化問題行為的關(guān)系, 刺激尋求理論認(rèn)為, 較低的皮質(zhì)醇水平對(duì)兒童來說可能是一種不愉快的生理狀態(tài), 因此兒童會(huì)通過尋找刺激提高生理喚醒(Zuckerman, 1979)。而恐懼缺乏理論認(rèn)為, 皮質(zhì)醇基線低說明HPA系統(tǒng)處于低喚醒狀態(tài),這類個(gè)體在各種情境中很少表現(xiàn)害怕與焦慮, 因此更可能出現(xiàn)外化問題行為(Raine, 2002)。學(xué)齡前兒童和學(xué)齡期兒童外化問題行為與皮質(zhì)醇相反的關(guān)系可能因?yàn)閮和霈F(xiàn)外化問題行為的種類不同,學(xué)齡前兒童多表現(xiàn)出攻擊性行為, 而學(xué)齡期兒童則常選擇言語攻擊。而青春期是一個(gè)大腦重組的過程(Sisk ＆amp; Zehr, 2005), 生理發(fā)育可能會(huì)影響激素與行為的關(guān)系, 且同伴關(guān)系在青春期兒童生活中所占比重增加等社會(huì)因素也可能對(duì)兒童皮質(zhì)醇與行為關(guān)系產(chǎn)生影響(Alink et al., 2008), 因此青少年中皮質(zhì)醇與外化問題行為的關(guān)系并不顯著。由于外化問題行為在性別方面顯示出較大的差異,因此研究者也關(guān)注皮質(zhì)醇與外化問題之間關(guān)系與性別的關(guān)系, 其中國(guó)外研究多關(guān)注男性群體中皮質(zhì)醇與外化問題行為的關(guān)系。而我國(guó)則有研究發(fā)現(xiàn), 男性攻擊行為與他們午間皮質(zhì)醇濃度呈負(fù)相關(guān), 而在女性中并未發(fā)現(xiàn)這種關(guān)系(余毅震,黃艷,史俊霞, 2007)。

表2 兒童皮質(zhì)醇日常節(jié)律與外化問題行為的關(guān)系研究

綜合上述皮質(zhì)醇與兒童內(nèi)外化問題行為的研究, 認(rèn)為存在差異可能有以下原因：首先, 不同研究對(duì)皮質(zhì)醇的測(cè)量方式存在差異。唾液皮質(zhì)醇與血液皮質(zhì)醇對(duì)壓力的反應(yīng)速度存在差異, 雖然唾液皮質(zhì)醇與血液皮質(zhì)醇存在高相關(guān)(Putignano et al., 2003), 但唾液皮質(zhì)醇通常在壓力后約20分鐘達(dá)到頂峰(謝曉飛, 王莉, 孫小舒, 2009), 而血液皮質(zhì)醇在壓力條件下變化速度相對(duì)較慢。因此研究需要針對(duì)不同的研究目的選用唾液皮質(zhì)醇、血液皮質(zhì)醇等不同的測(cè)量方式。其次, 需要考慮兒童的問題行為是否具有臨床效度, 即行為的嚴(yán)重程度及該問題行為是否達(dá)到臨床診斷標(biāo)準(zhǔn)會(huì)對(duì)兒童的壓力反應(yīng)造成影響。例如, 抑郁癥患者和正常兒童的內(nèi)化問題行為與皮質(zhì)醇的關(guān)系強(qiáng)弱不同(Halligan et al., 2007; Ruttle at al., 2011); 而具有反社會(huì)行為的兒童和一般兒童的外化問題行為與皮質(zhì)醇水平的關(guān)系卻恰恰相反(Mc Burnett et al.,2000; Van Bokhoven et al., 2005)。第三, 研究需要根據(jù)不同的目的選擇不同的類型(橫斷研究或縱向研究), 橫斷研究多反映當(dāng)下的問題行為與壓力系統(tǒng)的關(guān)系, 而縱向研究則可預(yù)測(cè)問題行為對(duì)皮質(zhì)醇水平的影響。最后, 皮質(zhì)醇的測(cè)量時(shí)期也可能造成研究差異的出現(xiàn), 在研究的第一階段測(cè)量皮質(zhì)醇, 反映的是生理活動(dòng)對(duì)問題行為的預(yù)測(cè)作用(Shirtcliff ＆amp; Essex, 2008; Sondeijker et al., 2008),而在追蹤測(cè)查階段測(cè)量皮質(zhì)醇, 則反映了兒童問題行為對(duì)生理活動(dòng)的影響(McBurnett et al., 2000;Ruttle at al., 2011)。因此在縱向研究中, 需要謹(jǐn)慎的選擇皮質(zhì)醇的測(cè)量時(shí)期。

2 兒童心理社會(huì)因素與皮質(zhì)醇

長(zhǎng)期對(duì)動(dòng)物和人的研究表明, 早期的生活壓力(0～6歲)對(duì)于HPA軸有長(zhǎng)期的影,且這種影響主要取決于壓力持續(xù)的時(shí)間和強(qiáng)度(Fisher, Gunnar,Dozier, Bruce, ＆amp; Pears, 2006; Miklós ＆amp; Kovács,2012) (見表 3)。動(dòng)物模型發(fā)現(xiàn), 極度不良的早期照顧會(huì)加快小鼠的腦細(xì)胞死亡(Zhang et al., 2002),且刺激促腎上腺皮質(zhì)激素的釋放, 從而干擾海馬的發(fā)育(Fenoglio, Brunson, ＆amp; Baram, 2006)。在人類研究中也發(fā)現(xiàn)了相似的結(jié)論(Cicchetti et al.,2010)。這可能因?yàn)? 慢性壓力會(huì)增加杏仁核產(chǎn)生的促腎上腺激素釋放激素, 提高與恐懼和焦慮情緒有關(guān)的受體的表達(dá)(Sanchez, Ladd, ＆amp; Plotsky, 2001),而海馬、杏仁核這些邊緣系統(tǒng)和前額葉皮層在五歲前都有飛速的發(fā)展(Thompson ＆amp; Nelson, 2001)。因此, 早期的壓力和虐待會(huì)影響神經(jīng)系統(tǒng)的發(fā)育(Cicchetti ＆amp; Rogosch, 2001; Gunnar ＆amp; Vazquez,2006); 而早期不良照顧導(dǎo)致的較高恐懼和 HPA軸系統(tǒng)的過度激活會(huì)增加生命過程中的適應(yīng)負(fù)荷,使個(gè)體在以后的發(fā)展過程中面對(duì)壓力時(shí)更容易受到情緒障礙的影響(McEwen, 2003; McEwen ＆amp;Stellar, 1993)。

表3 兒童心理社會(huì)因素與皮質(zhì)醇的關(guān)系研究

2.1 受虐待經(jīng)歷與皮質(zhì)醇

研究者關(guān)注早期受虐待經(jīng)歷(0～6歲)對(duì)兒童皮質(zhì)醇影響時(shí), 往往會(huì)考慮兒童的問題行為。例如, 兒童早期受虐待的時(shí)間、類型均會(huì)影響兒童HPA軸的發(fā)展和內(nèi)化問題行為的產(chǎn)生(Cicchetti et al., 2010)。Cicchetti等人發(fā)現(xiàn), 經(jīng)歷早期軀體虐待的兒童, 日常皮質(zhì)醇濃度的降低往往伴隨著較高的內(nèi)化問題行為, 而早期經(jīng)歷忽視和情緒虐待往往則不會(huì)引起HPA軸的失調(diào)。此外, 兒童5歲后受虐待對(duì)HPA軸的影響顯著低于5歲前, 因此無法預(yù)測(cè)5歲后受軀體虐待或性虐待的兒童皮質(zhì)醇水平與抑郁、焦慮等內(nèi)化問題行為的關(guān)系。這可能是因?yàn)? 對(duì)于僅僅被忽視的兒童, 被忽視并沒有導(dǎo)致恐懼或者威脅的增加, 因此不會(huì)對(duì)HPA軸活動(dòng)產(chǎn)生顯著影響。而和年齡大的兒童相比, 年齡較小的受虐待兒童缺乏對(duì)于外界攻擊的預(yù)測(cè),對(duì)于攻擊過度警覺可能讓他們處于慢性壓力當(dāng)中,神經(jīng)內(nèi)分泌系統(tǒng)發(fā)育受到影響, 而這種神經(jīng)內(nèi)分泌失調(diào)可能是抑郁產(chǎn)生的原因之一(Cicchetti et al.,2010)。

2.2 父母教養(yǎng)方式與皮質(zhì)醇

除了早期經(jīng)歷, 父母教養(yǎng)方式也會(huì)對(duì)皮質(zhì)醇產(chǎn)生影響。以往關(guān)于父母教養(yǎng)方式與皮質(zhì)醇水平的研究, 主要集中在積極和消極方面的教養(yǎng)因素如何影響兒童特定時(shí)間的皮質(zhì)醇水平及每日的皮質(zhì)醇水平變化趨勢(shì), 并發(fā)現(xiàn)過多的消極父母教養(yǎng)因素, 如監(jiān)管不力、消極關(guān)注等教養(yǎng)方式與兒童較低的晨起皮質(zhì)醇水平和平緩的晝夜節(jié)律有關(guān)(Martin et al., 2014), 而缺乏積極的父母教養(yǎng)方式(如對(duì)兒童需求不敏感)也可以預(yù)測(cè)平緩的皮質(zhì)醇水平(Zalewski et al., 2012)。

皮質(zhì)醇除了與父母教養(yǎng)方式直接相關(guān), 且在父母教養(yǎng)方式與兒童認(rèn)知、情緒、行為發(fā)展間存在中介作用(Blair, Granger et al., 2011; Martin et al., 2014)。研究發(fā)現(xiàn), 不良的父母教養(yǎng)方式會(huì)導(dǎo)致兒童更多的暴露于壓力環(huán)境中, 缺少緩沖和安慰;長(zhǎng)期處于應(yīng)激狀態(tài)會(huì)使應(yīng)激生理系統(tǒng)達(dá)到高負(fù)荷狀態(tài), 產(chǎn)生適應(yīng)性的過分活躍或活動(dòng)不足, 妨礙激素調(diào)節(jié)的靈活性, 而這種靈活性又與兒童的執(zhí)行功能存在關(guān)聯(lián)(McEwen, 2000; Ramos ＆amp; Arnsten,2007)。例如, Martin等人(2014)發(fā)現(xiàn)皮質(zhì)醇的日常節(jié)律能夠部分解釋父母教養(yǎng)方式對(duì)兒童外化問題行為的影響, 即不良的父母教養(yǎng)方式會(huì)通過減緩兒童皮質(zhì)醇節(jié)律而增加兒童的外化問題行為。此外, 如果母親對(duì)于兒童的教養(yǎng)方式不合理, 給予的回應(yīng)很少或者過度控制, 都會(huì)使兒童皮質(zhì)醇分泌變得平緩(Pendry ＆amp; Adam, 2007; Zalewski et al.,2012), 而平緩的晝夜皮質(zhì)醇節(jié)律又與較高的外化問題行為有關(guān)(Ruttle et al., 2011)?？梢? 父母教養(yǎng)方式可能通過影響兒童的生理機(jī)能進(jìn)一步影響兒童認(rèn)知、情緒和行為的發(fā)展。

2.3 貧困與皮質(zhì)醇

已有研究表明家庭社會(huì)經(jīng)濟(jì)地位與兒童的應(yīng)激生理反應(yīng)變化, 以及兒童的發(fā)展之間也存在關(guān)聯(lián)。一個(gè)可能的機(jī)制是, 貧困通過壓力破壞兒童的內(nèi)穩(wěn)態(tài)系統(tǒng), 從而影響兒童的發(fā)展。一項(xiàng)長(zhǎng)期的追蹤研究發(fā)現(xiàn), 生活在貧困中的時(shí)間與適應(yīng)負(fù)荷的提高有關(guān), 而較高的適應(yīng)負(fù)荷可能加重貧困對(duì)兒童執(zhí)行功能特別是工作記憶的損傷(Evans ＆amp;Schamberg, 2009)。然而, 目前關(guān)于貧困與兒童皮質(zhì)醇變化的研究結(jié)果并不一致。有研究發(fā)現(xiàn), 雖然長(zhǎng)期的壓力源會(huì)導(dǎo)致HPA軸活動(dòng)減弱, 皮質(zhì)醇水平降低(Fisher, Van Ryzin, ＆amp; Gunnar, 2011), 但也有研究發(fā)現(xiàn)低收入家庭兒童具有較高的皮質(zhì)醇水平(Evans, 2003; Evans＆amp; Kim, 2007), 還有研究認(rèn)為偏高或偏低的皮質(zhì)醇水平在具有貧困等不利經(jīng)歷的兒童身上都可能出現(xiàn)(Blair, Raver et al.,2011)。其中, 多數(shù)研究發(fā)現(xiàn)家庭極度貧困的學(xué)齡前兒童皮質(zhì)醇基線水平較低(Lupien et al., 2001),其面臨的經(jīng)濟(jì)壓力與較低的日常皮質(zhì)斜率正相關(guān)(Badanes et al., 2011), 低收入家庭中兒童和青少年HPA軸的活動(dòng)加劇可能是由貧困帶來的壓力積累破壞了壓力調(diào)節(jié)機(jī)制引起的。但也有研究表明,與正常兒童相比, 貧困兒童早晨皮質(zhì)醇水平較高(Lupien et al., 2001)。

可見貧困對(duì)于兒童日常皮質(zhì)醇節(jié)律的影響存在爭(zhēng)議。一種可能是, 貧困對(duì)于皮質(zhì)醇日常節(jié)律的影響依據(jù)個(gè)體差異有兩種表現(xiàn)：在貧困條件下,一部分人表現(xiàn)出基線升高, 一部分人表現(xiàn)為基線降低, 但差異存在的原因有待探究(Blair, Raver,Granger, Mills-Koonce, Hibel, ＆amp; Investigators,2011)。另一種可能是, 在考慮貧困對(duì)皮質(zhì)醇的影響時(shí), 需要關(guān)注貧困持續(xù)的時(shí)間和貧困程度。雖然過度的壓力會(huì)損傷神經(jīng)內(nèi)分泌系統(tǒng)的功能(Aschbacher et al., 2013; Du et al., 2009; Gustafsson, Anckars?ter,Lichtenstein, Nelson, ＆amp; Gustafsson, 2010; Slatcher＆amp; Robles, 2012), 但適度的壓力卻能夠提高個(gè)體的生理彈性, 使個(gè)體在應(yīng)激條件下做出適應(yīng)性的反應(yīng)(McEwen, 2004; Michels et al., 2012; Ouellet-Morin et al., 2011)。為了解釋壓力持續(xù)時(shí)間對(duì)個(gè)體的影響, 適應(yīng)負(fù)荷理論指出, 機(jī)體的穩(wěn)態(tài)能夠幫助個(gè)體通過一系列的調(diào)節(jié)活動(dòng)在環(huán)境中保持體內(nèi)穩(wěn)定(Sapolsky, 2004)。如果穩(wěn)態(tài)系統(tǒng)面臨的壓力過大或過于頻繁, 則機(jī)體的穩(wěn)態(tài)系統(tǒng)則會(huì)被干擾,導(dǎo)致 HPA軸功能失調(diào); 而在支持性的環(huán)境下, 皮質(zhì)醇基線處在一個(gè)適度的范圍內(nèi), 并對(duì)刺激做出反應(yīng), 從而建立了一個(gè)急性應(yīng)激條件下所需要的靈活的升高和降低反應(yīng)(Flier, Underhill, ＆amp; McEwen,1998; McEwen, 2000)。因此, 未來對(duì)于貧困與兒童皮質(zhì)醇的研究應(yīng)該考慮貧困的程度和貧困持續(xù)的時(shí)間。

2.4 同伴關(guān)系與皮質(zhì)醇

隨著年齡的增長(zhǎng), 兒童逐步開始社會(huì)性生活,因此從童年早期(3～6歲)開始, 皮質(zhì)醇的節(jié)律就會(huì)受到社會(huì)環(huán)境的影響(Gunnar ＆amp; Quevedo, 2007),而作為兒童社會(huì)環(huán)境的重要組成部分, 同伴關(guān)系也會(huì)對(duì)兒童皮質(zhì)醇造成一定的影響(表3)。有研究發(fā)現(xiàn)兒童在幼兒園中的下午皮質(zhì)醇水平比在家時(shí)更高(Vermeer ＆amp; van Ijzendoorn, 2006); 且和正常情況下個(gè)體下午的皮質(zhì)醇水平逐漸下降的情況不同,兒童在幼兒園中皮質(zhì)醇水平呈上升趨勢(shì)(Watamura,Donzella, Alwin, ＆amp; Gunnar, 2003)。這可能因?yàn)閷W(xué)齡前兒童(3～7歲)的社會(huì)交往能力和認(rèn)知能力并不成熟, 而學(xué)齡前兒童在幼兒園從事的交往活動(dòng)要比家里更多, 因此交往活動(dòng)有可能成為主要的認(rèn)知源(謝曉飛等, 2009)。還有研究表明, 同伴地位和同伴接受程度均會(huì)影響兒童的皮質(zhì)醇水平,同伴地位較低的 15歲兒童早晨皮質(zhì)醇水平較低(West et al., 2010), 而遭受同伴拒絕越多的兒童,他們的早晚皮質(zhì)醇的分泌量要高于其他兒童(Gunnar et al., 2003)?？赡艿脑蚴? 在與同伴交往的過程中, 遭受同伴拒絕的兒童會(huì)體驗(yàn)到更多的負(fù)面體驗(yàn)(包括拒絕與排斥), 由于害怕遭到這些負(fù)面體驗(yàn), 這些兒童的HPA系統(tǒng)會(huì)處于高度喚醒狀態(tài), 從而引起皮質(zhì)醇水平升高。

此外, 同伴問題對(duì)皮質(zhì)醇的影響存在年齡和性別差異。在學(xué)齡期兒童(5～10歲)中, 男生同伴問題與較高的晨起皮質(zhì)醇和皮質(zhì)醇節(jié)律陡峭有關(guān),而女生的同伴問題往往伴隨著較低的皮質(zhì)醇基線(Michels et al., 2012)?？赡艿脑蚴桥鶎?duì)同伴關(guān)系更敏感, 更容易在同伴關(guān)系中感覺到壓力(Rose ＆amp; Rudolph, 2006)。因此, 女生的同伴問題很有可能使她們處于長(zhǎng)期壓力下, 從而擾亂皮質(zhì)醇節(jié)律。

綜上, 可見兒童受虐待經(jīng)歷、家庭教養(yǎng)方式、社會(huì)經(jīng)濟(jì)地位、同伴關(guān)系都會(huì)對(duì)皮質(zhì)醇活動(dòng)產(chǎn)生影響。除此之外, 兒童近期生活壓力、父母精神狀況、是否被收養(yǎng)及種族因素也可能對(duì)兒童產(chǎn)生影響(Brennan et al., 2008; Gustafsson et al.,2010; Laurent et al., 2014; Lupien, King, Meany, ＆amp;Bruce, 2000; Martin et al., 2014)。這些環(huán)境因素不僅直接影響兒童皮質(zhì)醇活動(dòng), 也會(huì)相互作用并對(duì)兒童產(chǎn)生影響。例如, Zalewski等人(2012)的研究顯示, 貧困可能通過與父母教養(yǎng)方式的交互作用影響兒童皮質(zhì)醇水平, 而 Blair等人(2011)在分析了大量有關(guān)貧困等不利環(huán)境與兒童皮質(zhì)醇水平的關(guān)系后, 認(rèn)為好的父母教養(yǎng)方式可以對(duì)壓力環(huán)境對(duì)兒童的不良影響起調(diào)節(jié)作用。

3 不足與展望

西方研究者對(duì)皮質(zhì)醇和心理社會(huì)因素及兒童問題行為關(guān)系的研究到目前為止取得了較為豐碩的成果, 發(fā)現(xiàn)兒童皮質(zhì)醇日常節(jié)律與兒童行為相關(guān), 并受到環(huán)境因素的影響, 是多種因素交叉共同作用的結(jié)果。但由于以往研究的存在的一些不足, 未來研究還有進(jìn)一步拓展的空間：

第一, 皮質(zhì)醇與內(nèi)外化問題的關(guān)系仍不明確。在對(duì)兒童行為問題進(jìn)行研究時(shí), 應(yīng)該考慮群體的特殊性、癥狀是否達(dá)到臨床水平以及是否采用縱向研究。且關(guān)于皮質(zhì)醇與內(nèi)化問題關(guān)系的研究多集中在HPA軸活動(dòng)與兒童整體表現(xiàn)出的內(nèi)化問題或抑郁這個(gè)單一水平的關(guān)系上, 很少考慮焦慮、低自尊等內(nèi)化問題與皮質(zhì)醇的關(guān)系, 因此未來研究應(yīng)該通過多種指標(biāo)對(duì)內(nèi)化問題進(jìn)行評(píng)估。

其次, 目前對(duì)心理社會(huì)因素的研究多集中于探討家庭、學(xué)校等環(huán)境因素對(duì)兒童皮質(zhì)醇活動(dòng)的影響, 且研究過程中較少考慮環(huán)境因素的特點(diǎn)及各因素的交互作用。雖然已有針對(duì)貧困兒童的研究表明, 家庭中積極教養(yǎng)方式的缺失對(duì)應(yīng)激條件下皮質(zhì)醇活動(dòng)的影響大于消極教養(yǎng)方式的出現(xiàn)(Blair, Granger et al., 2011)。但積極關(guān)注、積極互動(dòng)、情感支持、干涉行為、疏離程度等家庭教養(yǎng)因素以及同伴支持、教師支持等社會(huì)因素對(duì)貧困、受虐待等處境不利的兒童日常皮質(zhì)醇活動(dòng)的影響仍然有待探討。此外, 在關(guān)注環(huán)境因素對(duì)皮質(zhì)醇的影響時(shí), 應(yīng)該特別考慮由于環(huán)境所導(dǎo)致的壓力產(chǎn)生的時(shí)期、持續(xù)的時(shí)間以及壓力強(qiáng)度的穩(wěn)定性, 并區(qū)分不同環(huán)境因素對(duì)兒童造成的不同壓力。因此, 未來研究需要進(jìn)一步明確環(huán)境因素對(duì)兒童皮質(zhì)醇活動(dòng)的影響, 分別探討家庭(教養(yǎng)方式)、社會(huì)(同伴關(guān)系、師生關(guān)系)等因素對(duì)兒童的保護(hù)性作用。同時(shí), 也應(yīng)該關(guān)注因素之間的關(guān)系,探討不同環(huán)境因素的交互作用對(duì)兒童皮質(zhì)醇活動(dòng)的影響。

第三, 多數(shù)研究只關(guān)注皮質(zhì)醇與行為的關(guān)系,或只關(guān)注影響兒童皮質(zhì)醇的因素, 很少同時(shí)考慮三者之間的交互作用。少數(shù)研究表明, HPA軸可能在環(huán)境與兒童內(nèi)外化行為問題中起到一定的中介和調(diào)節(jié)作用。例如, Laurent等人(2014)發(fā)現(xiàn)對(duì)于晚間皮質(zhì)醇濃度較高的兒童, 他們的父母的抑郁癥狀與兒童內(nèi)外化問題行為的關(guān)系更強(qiáng), 即父母單獨(dú)的抑郁癥狀和二者的交互作用都可能對(duì)晚間高皮質(zhì)醇水平的兒童造成較大的影響。另外, 皮質(zhì)醇在貧困與父母教養(yǎng)方式間也可能起到中介作用。例如, 貧困可能通過減弱父母溫情程度、協(xié)助與支持因素, 增強(qiáng)消極教養(yǎng)方式使得兒童晝夜皮質(zhì)醇的節(jié)律減緩, 進(jìn)而降低兒童的自我控制能力(Zalewski et al., 2012)。因此, 未來研究可以在以往對(duì)早期負(fù)性經(jīng)歷、貧困、父母教養(yǎng)方式對(duì)兒童情緒、行為的影響研究基礎(chǔ)上, 探索環(huán)境因素對(duì)兒童情緒、行為影響的生理機(jī)制, 即探索環(huán)境-生理-行為的系統(tǒng)變化, 為兒童問題行為的預(yù)防干預(yù)提供心理學(xué)支持。

最后, 未來研究也可將皮質(zhì)醇作為生物學(xué)指標(biāo)用于干預(yù)效果的評(píng)估。隨著生理測(cè)量技術(shù)的發(fā)展, 越來越多的研究開始關(guān)注干預(yù)對(duì)個(gè)體生理機(jī)能產(chǎn)生的影響(Fisher, Chamberlain, ＆amp; Leve, 2009;Bernard et al., 2012)。例如, Fisher等人(2011)使用寄養(yǎng)兒童的晝夜皮質(zhì)醇節(jié)律評(píng)估基于照顧者的干預(yù)項(xiàng)目的干預(yù)效果。結(jié)果發(fā)現(xiàn)與控制組兒童相比,干預(yù)組的兒童在寄養(yǎng)地點(diǎn)變化時(shí)并沒有出現(xiàn)皮質(zhì)醇晝夜節(jié)律失調(diào)。此外, 研究還發(fā)現(xiàn), 如果寄養(yǎng)兒童的照顧者進(jìn)行干預(yù), 則可以減輕照顧者在應(yīng)對(duì)兒童問題行為時(shí)感知到的壓力, 并緩解HPA軸的失調(diào)。因此, 未來國(guó)內(nèi)研究也可以使用皮質(zhì)醇作為生物學(xué)指標(biāo)對(duì)干預(yù)效果進(jìn)行評(píng)估。

黃希庭, 楊治良, 林崇德. (2003).心理學(xué)大辭典.上海:上海教育出版社

謝曉飛, 王莉, 孫小舒. (2009). 皮質(zhì)醇反應(yīng)與兒童社會(huì)情緒適應(yīng)(綜述).中國(guó)心理衛(wèi)生雜志, 23(3), 220–223.

余毅震, 黃艷, 史俊霞. (2007). 青少年攻擊行為與內(nèi)分泌因素關(guān)系的研究.中國(guó)婦幼保健, 22(14), 1909–1911.

Achenbach, T. (1991).Child behavior checklist/4-18. Burlington:University of Vermont,

Alink, L. R., Van IJzendoorn, M. H., Bakermans-Kranenburg, M.J., Mesman, J., Juffer, F., ＆amp; Koot, H. M. (2008). Cortisol and externalizing behavior in children and adolescents: Mixed meta-analytic evidence for the inverse relation of basal cortisol and cortisol reactivity with externalizing behavior.Developmental Psychobiology, 50(5), 427–450.

Aschbacher, K., O’Donovan, A., Wolkowitz, O. M., Dhabhar,F. S., Su, Y., ＆amp; Epel, E. (2013). Good stress, bad stress and oxidative stress: Insights from anticipatory cortisol reactivity.Psychoneuroendocrinology, 38(9), 1698–1708.

Badanes, L. S., Watamura, S. E., ＆amp; Hankin, B. L. (2011).Hypocortisolism as a potential marker of allostatic load in children: Associations with family risk and internalizing disorders.Development and Psychopathology, 23(3), 881–896.

Bernard, K., Dozier, M., Bick, J., Lewis-Morrarty, E.,Lindhiem, O., ＆amp; Carlson, E. (2012). Enhancing attachment organization among maltreated children: Results of a randomized clinical trial.Child Development, 83(2), 623–636.

Blair, C., Granger, D. A., Willoughby, M., Mills-Koonce, R.,Cox, M., Greenberg, M. T., … Fortunato, C. F. (2011).Salivary cortisol mediates effects of poverty and parenting on executive functions in early childhood.Child Development, 82(6), 1970–1984.

Blair, C., Raver, C. C., Granger, D., Mills-Koonce, R., Hibel,L., ＆amp; Investigators, F. L. P. K. (2011). Allostasis and allostatic load in the context of poverty in early childhood.Development and Psychopathology, 23(3), 845–857.

Brennan, P. A., Pargas, R., Walker, E. F., Green, P., Newport,D. J., ＆amp; Stowe, Z. (2008). Maternal depression and infant cortisol: Influences of timing, comorbidity and treatment.Journal of Child Psychology and Psychiatry, 49(10),1099–1107.

Chida, Y., ＆amp; Steptoe, A. (2009). Cortisol awakening response and psychosocial factors: A systematic review and meta-analysis.Biological Psychology, 80(3), 265–278.

Chrousos, G. P. (2009). Stress and disorders of the stress system.Nature Reviews Endocrinology, 5(7), 374–381.

Cicchetti, D., ＆amp; Rogosch, F. A. (2001). The impact of child maltreatment and psychopathology on neuroendocrine functioning.Development and Psychopathology, 13(4),783–804.

Cicchetti, D., Rogosch, F. A., Gunnar, M. R., ＆amp; Toth, S. L.(2010). The differential impacts of early physical and sexual abuse and internalizing problems on daytime cortisol rhythm in school-aged children.Child Development, 81(1),252–269.

Claes, S. J. (2004). Corticotropin-releasing hormone (CRH)in psychiatry: From stress to psychopathology.Annals of Medicine, 36(1), 50–61.

De Bellis, M. D., Dahl, R. E., Perel, J. M., Birmaher, B.,Al-Shabbout, M., Williamson, D. E., … Ryan, N. D. (1996).Nocturnal ACTH, cortisol, growth hormone, and prolactin secretion in prepubertal depression.Journal of the American Academy of Child and Adolescent Psychiatry,35(9), 1130–1138.

Dockray, S., Susman, E. J., ＆amp; Dorn, L. D. (2009).Depression, cortisol reactivity, and obesity in childhood and adolescence.Journal of Adolescent Health, 45(4),344-350.

Du, J., Wang, Y., Hunter, R., Wei, Y. L., Blumenthal, R.,Falke, C., … Manji, H. K. (2009). Dynamic regulation of mitochondrial function by glucocorticoids.Proceedings of the National Academy of Sciences of the United States of America, 106(9), 3543–3548.

Evans, G. W. (2003). A multimethodological analysis of cumulative risk and allostatic load among rural children.Developmental Psychology, 39(5), 924–933.

Evans, G. W., ＆amp; Kim, P. (2007). Childhood poverty and health cumulative risk exposure and stress dysregulation.Psychological Science, 18(11), 953–957.

Evans, G. W., ＆amp; Schamberg, M. A. (2009). Childhood poverty, chronic stress, and adult working memory.Proceedings of the National Academy of Sciences of the United States of America, 106(16), 6545–6549.

Fenoglio, K. A., Brunson, K. L., ＆amp; Baram, T. Z. (2006).Hippocampal neuroplasticity induced by early-life stress:Functional and molecular aspects.Frontiers in Neuroendocrinology, 27(2), 180–192.

Fisher, P. A., Chamberlain, P., ＆amp; Leve, L. D. (2009). Improving the lives of foster children through evidenced-based interventions.Vulnerable Children and Youth Studies, 4(2),122–127.

Fisher, P. A., Gunnar, M. R., Dozier, M., Bruce, J., ＆amp; Pears,K. C. (2006). Effects of therapeutic interventions for foster children on behavioral problems, caregiver attachment,and stress regulatory neural systems.Annals of the New York Academy of Sciences, 1094(1), 215–225.

Fisher, P. A., Van Ryzin, M. J., ＆amp; Gunnar, M. R. (2011).Mitigating HPA axis dysregulation associated with placement changes in foster care.Psychoneuroendocrinology, 36(4),531–539.

Flier, J. S., Underhill, L. H., ＆amp; McEwen, B. S. (1998).Protective and damaging effects of stress mediators.New England Journal of Medicine, 338(3), 171–179.

Fries, E., Hesse, J., Hellhammer, J., ＆amp; Hellhammer, D. H. (2005).A new view on hypocortisolism.Psychoneuroendocrinology,30(10), 1010–1016.

Goodyer, I. M., Herbert, J., Altham, P. M. E., Pearson, J.,Secher, S. M., ＆amp; Shiers, H. M. (1996). Adrenal secretion during major depression in 8- to 16-year-olds, I. Altered diurnal rhythms in salivary cortisol and dehydroepiandrosterone(DHEA) at presentation.Psychological Medicine, 26(2),245–256.

Goodyer, I. M., Park, R. J., ＆amp; Herbert, J. (2001). Psychosocial and endocrine features of chronic first-episode major depression in 8–16 year olds.Biological Psychiatry, 50(5),351–357.

Granger, D. A. (1998). Children's salivary cortisol,internalising behaviour problems, and family environment:Results from the Concordia Longitudinal Risk Project.International Journal of Behavioral Development, 22(4),707–728.

Greaves-Lord, K., Ferdinand, R. F., Oldehinkel, A. J.,Sondeijker, F. E., Ormel, J., ＆amp; Verhulst, F. C. (2007).Higher cortisol awakening response in young adolescents with persistent anxiety problems.Acta Psychiatrica Scandinavica, 116(2), 137–144.

Gunnar, M. R., ＆amp; Cheatham, C. L. (2003). Brain and behavior interfaces: Stress and the developing brain.Infant Mental Health Journal, 24(3), 195–211.

Gunnar, M. R., ＆amp; Quevedo, K. M. (2007). Early care experiences and HPA axis regulation in children: A mechanism for later trauma vulnerability.Progress in Brain Research, 167, 137–149.

Gunnar, M. R., Sebanc, A. M., Tout, K., Donzella, B., ＆amp; Van Dulmen, M. M. (2003). Peer rejection, temperament, and cortisol activity in preschoolers.Developmental Psychobiology,43(4), 346–368.

Gunnar, M. R., ＆amp; Vazquez, D. (2006). Stress neurobiology and developmental psychopathology. In D. Cichetti ＆amp; D. J.Cohen (Eds.),Developmental psychopathology(2nd ed.).New York: Wiley.

Gunnar, M. R., ＆amp; Vazquez, D. M. (2001). Low cortisol and a flattening of expected daytime rhythm: Potential indices of risk in human development.Development and Psychopathology, 13(3), 515–538.

Gustafsson, P. E., Anckars?ter, H., Lichtenstein, P., Nelson,N., ＆amp; Gustafsson, P. A. (2010). Does quantity have a quality all its own? Cumulative adversity and up-and downregulation of circadian salivary cortisol levels in healthy children.Psychoneuroendocrinology, 35(9), 1410–1415.

Halligan, S. L., Herbert, J., Goodyer, I., ＆amp; Murray, L. (2007).Disturbances in morning cortisol secretion in association with maternal postnatal depression predict subsequent depressive symptomatology in adolescents.Biological Psychiatry, 62(1), 40–46.

Heim, C., Ehlert, U., ＆amp; Hellhammer, D. H. (2000). The potential role of hypocortisolism in the pathophysiology of stress-related bodily disorders.Psychoneuroendocrinology,25(1), 1–35.

Holsboer, F. (2000). The corticosteroid receptor hypothesis of depression.Neuropsychopharmacology, 23(5), 477–501.

Kaufman, J. (1991). Depressive disorders in maltreated children.Journal of the American Academy of Child and Adolescent Psychiatry, 30(2), 257–265.

Laurent, H. K., Neiderhiser, J. M., Natsuaki, M. N., Shaw, D.S., Fisher, P. A., Reiss, D., ＆amp; Leve, L. D. (2014). Stress system development from age 4.5 to 6: Family environment predictors and adjustment implications of HPA activity stability versus change.Developmental Psychobiology,56(3), 340–354.

Lopez-Duran, N. L., Kovacs, M., ＆amp; George, C. J. (2009).Hypothalamic–pituitary–adrenal axis dysregulation in depressed children and adolescents: A meta-analysis.Psychoneuroendocrinology, 34(9), 1272–1283.

Lupien, S. J., King, S., Meaney, M. J., ＆amp; McEwen, B. S.(2000). Child’s stress hormone levels correlate with mother’s socioeconomic status and depressive state.Biological Psychiatry, 48(10), 976–980.

Lupien, S. J., King, S., Meaney, M. J., ＆amp; McEwen, B. S.(2001). Can poverty get under your skin? Basal cortisol levels and cognitive function in children from low and high socioeconomic status.Development and Psychopathology,13(3), 653–676.

Lupien, S. J., Maheu, F., Tu, M., Fiocco, A., ＆amp; Schramek, T.E. (2007). The effects of stress and stress hormones on human cognition: Implications for the field of brain and cognition.Brain and Cognition, 65(3), 209–237.

Marsman, R., Swinkels, S. H., Rosmalen, J. G., Oldehinkel,A. J., Ormel, J., ＆amp; Buitelaar, J. K. (2008). HPA-axis activity and externalizing behavior problems in early adolescents from the general population: The role of comorbidity and gender: The TRAILS study.Psychoneuroendocrinology,33(6), 789–798.

Martin, C. G., Kim, H. K., Bruce, J., ＆amp; Fisher, P. A. (2014). Child diurnal cortisol rhythms, parenting quality, and externalizing behaviors in preadolescence.Psychoneuroendocrinology, 40,170–180.

McBurnett, K., Lahey, B. B., Rathouz, P. J., ＆amp; Loeber, R.(2000). Low salivary cortisol and persistent aggression in boys referred for disruptive behavior.Archives of General Psychiatry, 57(1), 38–43.

McEwen, B. S. (2000). The neurobiology of stress: From serendipity to clinical relevance.Brain Research, 886(1-2),172–189.

McEwen, B. S. (2003). Mood disorders and allostatic load.Biological Psychiatry, 54(3), 200–207.

McEwen, B. S. (2004). Protection and damage from acute and chronic stress: Allostasis and allostatic overload and relevance to the pathophysiology of psychiatric disorders.Annals of the New York Academy of Sciences, 1032(1), 1–7.

McEwen, B. S., ＆amp; Stellar, E. (1993). Stress and the individual:Mechanisms leading to disease.Archives of Internal Medicine, 153(18), 2093–2101.

Michels, N., Sioen, I., Huybrechts, I., Bammann, K.,Vanaelst, B., De Vriendt, T., … De Henauw, S. (2012).Negative life events, emotions and psychological difficulties as determinants of salivary cortisol in Belgian primary school children.Psychoneuroendocrinology, 37(9), 1506–1515.

Miklós, I. H., ＆amp; Kovács, K. J. (2012). Reorganization of synaptic inputs to the hypothalamic paraventricular nucleus during chronic psychogenic stress in rats.Biological Psychiatry, 71(4), 301–308.

Miller, G. E., Chen, E., ＆amp; Zhou, E. S. (2007). If it goes up,must it come down? chronic stress and the hypothalamicpituitary-adrenocortical axis in humans.Psychological Bulletin, 133(1), 25–45.

Osika, W., Friberg, P., ＆amp; Wahrborg, P. (2007). A new short selfrating questionnaire to assess stress in children.International Journal of Behavioral Medicine, 14(2), 108–117.

Ouellet-Morin, I., Odgers, C. L., Danese, A., Bowes, L.,Shakoor, S., Papadopoulos, A. S., … Arseneault, L. (2011).Blunted cortisol responses to stress signal social and behavioral problems among maltreated/bullied 12-year-old children.Biological Psychiatry, 70(11), 1016–1023.

Pendry, P., ＆amp; Adam, E. K. (2007). Associations between parents' marital functioning, maternal parenting quality,maternal emotion and child cortisol levels.International Journal of Behavioral Development, 31(3), 218–231.

Pérez-Edgar, K., Schmidt, L. A., Henderson, H. A., Schulkin,J., ＆amp; Fox, N. A. (2008). Salivary cortisol levels and infant temperament shape developmental trajectories in boys at risk for behavioral maladjustment.Psychoneuroendocrinology,33(7), 916–925.

Plotsky, P. M., Owens, M. J., ＆amp; Nemeroff, C. B. (1998).Psychoneuroendocrinology of depression: Hypothalamicpituitary-adrenal axis.Psychiatric Clinics of North America,21(2), 293–307.

Poustka, L., Maras, A., Hohm, E., Fellinger, J., Holtmann,M., Banaschewski, T., … Laucht, M. (2010). Negative association between plasma cortisol levels and aggression in a high-risk community sample of adolescents.Journal of Neural Transmission, 117(5), 621–627.

Putignano, P., Toja, P., Dubini, A., Giraldi, F. P., Corsello, S. M.,＆amp; Cavagnini, F. (2003). Midnight salivary cortisol versus urinary free and midnight serum cortisol as screening tests for Cushing's syndrome.Journal of Clinical Endocrinology and Metabolism, 88(9), 4153–4157.

Raine, A. (2002). Biosocial studies of antisocial and violent behavior in children and adults: A review.Journal of Abnormal Child Psychology, 30(4), 311–326.

Ramos, B. P., ＆amp; Arnsten, A. F. (2007). Adrenergic pharmacology and cognition: Focus on the prefrontal cortex.Pharmacology and Therapeutics, 113(3), 523–536.

Rose, A. J., ＆amp; Rudolph, K. D. (2006). A review of sex differences in peer relationship processes: Potential trade-offs for the emotional and behavioral development of girls and boys.Psychological Bulletin, 132(1), 98–131.

Ruttle, P. L., Shirtcliff, E. A., Serbin, L. A., Ben-Dat Fisher, D.,Stack, D. M., ＆amp; Schwartzman, A. E. (2011). Disentangling psychobiological mechanisms underlying internalizing and externalizing behaviors in youth: Longitudinal and concurrent associations with cortisol.Hormones and Behavior, 59(1),123–132.

Sanchez, M., Ladd, C. O., ＆amp; Plotsky, P. M. (2001). Early adverse experience as a developmental risk factor for later psychopathology: Evidence from rodent and primate models.Development and Psychopathology, 13(03), 419–449.

Sapolsky, R. M. (2004). Social status and health in humans and other animals.Annual Review of Anthropology, 33,393–418.

Sapolsky, R. M., Romero, L. M., ＆amp; Munck, A. U. (2000). How do glucocorticoids influence stress responses? Integrating permissive, suppressive, stimulatory, and preparative actions 1.Endocrine Reviews, 21(1), 55–89.

Saxbe, D. E. (2008). A field (researcher's) guide to cortisol:Tracking HPA axis functioning in everyday life.Health Psychology Review, 2(2), 163–190.

Schmidt-Reinwald, A., Pruessner, J., Hellhammer, D.,Federenko, I., Rohleder, N., Schürmeyer, T., ＆amp; Kirschbaum,C. (1999). The cortisol response to awakening in relation to different challenge tests and a 12-hour cortisol rhythm.Life Sciences, 64(18), 1653–1660.

Shirtcliff, E. A., ＆amp; Essex, M. J. (2008). Concurrent and longitudinal associations of basal and diurnal cortisol with mental health symptoms in early adolescence.Developmental Psychobiology, 50(7), 690–703.

Shirtcliff, E. A., Granger, D. A., Booth, A., ＆amp; Johnson, D. (2005).Low salivary cortisol levels and externalizing behavior problems in youth.Development and Psychopathology,17(1), 167–184.

Shoal, G. D., Giancola, P. R., ＆amp; Kirillova, G. P. (2003). Salivary cortisol, personality, and aggressive behavior in adolescent boys: A 5-year longitudinal study.Journal of the American Academy of Child and Adolescent Psychiatry, 42(9),1101–1107.

Sisk, C. L., ＆amp; Zehr, J. L. (2005). Pubertal hormones organize the adolescent brain and behavior.Frontiers in Neuroendocrinology,26(3), 163–174.

Slatcher, R. B., ＆amp; Robles, T. F. (2012). Preschoolers'everyday conflict at home and diurnal cortisol patterns.Health Psychology, 31(6), 834–838.

Smider, N., Essex, M., Kalin, N., Buss, K., Klein, M.,Davidson, R., ＆amp; Goldsmith, H. H. (2002). Salivary cortisol as a predictor of socioemotional adjustment during kindergarten:A prospective study.Child Development, 73(1), 75–92.

Sondeijker, F. E., Ferdinand, R. F., Oldehinkel, A. J.,Tiemeier, H., Ormel, J., ＆amp; Verhulst, F. C. (2008). HPA-axis activity as a predictor of future disruptive behaviors in young adolescents.Psychophysiology, 45(3), 398–404.

Sondeijker, F. E., Ferdinand, R. F., Oldehinkel, A. J.,Veenstra, R., Tiemeier, H., Ormel, J., ＆amp; Verhulst, F. C.(2007). Disruptive behaviors and HPA-axis activity in young adolescent boys and girls from the general population.Journal of Psychiatric Research, 41(7), 570–578.

Thompson, R. A., ＆amp; Nelson, C. A. (2001). Developmental science and the media: Early brain development.American Psychologist, 56(1), 5–15

Van Bokhoven, I., Van Goozen, S. H. M., Van Engeland, H.,Schaal, B., Arseneault, L., Séguin, J. R., …Tremblay, R. E.(2005). Salivary cortisol and aggression in a populationbased longitudinal study of adolescent males.Journal of Neural Transmission, 112(8), 1083–1096.

Vermeer, H. J., ＆amp; Van Ijzendoorn, M. H. (2006). Children's elevated cortisol levels at daycare: A review and metaanalysis.Early Childhood Research Quarterly, 21(3),390–401.

Vigil, J. M., Geary, D. C., Granger, D. A., ＆amp; Flinn, M. V.(2010). Sex differences in salivary cortisol, alpha-amylase,and psychological functioning following hurricane katrina.Child Development, 81(4), 1228–1240.

Watamura, S. E., Donzella, B., Alwin, J., ＆amp; Gunnar, M. R.(2003). Morning-to-afternoon increases in cortisol concentrations for infants and toddlers at child care: Age differences and behavioral correlates.Child Development,74(4), 1006–1020.

Watamura, S. E., Sebanc, A. M., ＆amp; Gunnar, M. R. (2002).Rising cortisol at childcare: Relations with nap, rest, and temperament.Developmental Psychobiology, 40(1), 33–42.

West, P., Sweeting, H., Young, R., ＆amp; Kelly, S. (2010). The relative importance of family socioeconomic status and school-based peer hierarchies for morning cortisol in youth: An exporatory study.Social Science and Medicine,70(8), 1246–1253.

Wilhelm, I., Born, J., Kudielka, B. M., Schlotz, W., ＆amp; Wüst,S. (2007). Is the cortisol awakening rise a response to awakening?Psychoneuroendocrinology, 32(4), 358–366.

Zalewski, M., Lengua, L. J., Fisher, P. A., Trancik, A., Bush,N. R., ＆amp; Meltzoff, A. N. (2012). Poverty and single parenting:Relations with preschoolers' cortisol and effortful control.Infant and Child Development, 21(5), 537–554.

Zhang, L.-X., Levine, S., Dent, G., Zhan, Y., Xing, G.,Okimoto, D., …Smith, M. A.(2002). Maternal deprivation increases cell death in the infant rat brain.Developmental Brain Research, 133(1), 1–11.

Zuckerman, M. (1979).Sensation seeking: Beyond the optimal level of arousal. NJ: Erlbaum Hillsdale.