铅是具有多器官毒性的重金属，在人体内没有任何生理作用。正常人的身体里原本不应该含有铅，只是由于现代工业的发展，含铅物品的广泛使用以及环境污染的日积月累，我们与铅接触的机会越来越多，致使一部分铅尘侵入机体，使我们的血液、组织中或多或少含有了铅，学界将这一病理过程称为“铅暴露”或“铅接触”。
悲观主义是一个人的性格特性，一旦产生了悲观主义情绪，那么我们更倾向于会得到一些消极的后果。与乐观主义者相比，悲观主义者是一些抑郁等精神疾病以及慢性疾病（如心血管疾病）的高危人群。近日，一项主要针对成年男性展开的调查表明：持续性的铅暴露会引发人们产生悲观的人生观，甚至会增加人们患上抑郁等精神疾病的风险。相关研究论文发表在《美国流行病学》杂志上。
被铅污染的土壤、剥脱的含铅油漆皮以及香烟都是铅暴露的主要来源。铅进入人体后，仅有一小部分会被代谢排出，其余大部分铅会沉积在骨骼中。因此，检测骨骼中的铅的总量可以大致反映出一个人曾经暴露的铅总量。铅主要是影响人们神经系统，也可以增加心血管等疾病的发病风险。
在这项最新研究中，研究人员将铅视为一独立因素，着重考察了铅是否会影响人们悲观主义的产生。参与该项研究的志愿者主要是马萨诸塞州波士顿地区年龄在70岁左右的男性，工作人员在评价他们是倾向于悲观主义还是乐观主义后，收集了参试者在孩提时期及成年后的社会经济资料，同时测量了志愿者体内下肢胫骨中铅的含量。
结果发现那些骨骼中含铅较高的男性更有可能是悲观主义者。即使排除了他们在孩提和成年时期的社会经济情况的因素后，铅暴露与悲观主义之间的联系仍然是成立的。这就表明铅，作为一个独立的影响因素，与悲观主义的产生是有着密切相关性的。
Childhood and Adult Socioeconomic Position, Cumulative Lead Levels, and Pessimism in Later Life
Junenette L. Peters,Laura D. Kubzansky,Ai Ikeda,Avron Spiro III,Robert O. Wright,Marc G. Weisskopf,Daniel Kim,David Sparrow,et al.
Pessimism, a general tendency toward negative expectancies, is a risk factor for depression and also heart disease, stroke, and reduced cancer survival. There is evidence that individuals with higher lead exposure have poorer health. However, low socioeconomic status (SES) is linked with higher lead levels and greater pessimism, and it is unclear whether lead influences psychological functioning independently of other social factors. The authors considered interrelations among childhood and adult SES, lead levels, and psychological functioning in data collected on 412 Boston area men between 1991 and 2002 in a subgroup of the VA Normative Aging Study. Pessimism was measured by using the Life Orientation Test. Cumulative (tibia) lead was measured by x-ray fluorescence. Structural equation modeling was used to quantify the relations as mediated by childhood and adult SES, controlling for age, health behaviors, and health status. An interquartile range increase in lead quartile was associated with a 0.37 increase in pessimism score (P < 0.05). Low childhood and adult SES were related to higher tibia lead levels, and both were also independently associated with higher pessimism. Lead maintained an independent association with pessimism even after childhood and adult SES were considered. Results demonstrate an interrelated role of lead burden and SES over the life course in relation to psychological functioning in older age.
