13．Depression is not a choice．Rather，it is a true medical condition like high blood pressure or heart disease．In the United States alone，more than 17million people suffer from depression with women being twice as likely as men to suffer from the disease．Depression crosses racial and socioeconomic lines． Anyone can suffer from it，and those that do are not"crazy"or"weak"．They have a serious yet highly treatable disease．
Feeling down？You're not alone．If depression seems pretty common，it is．One in every ten adults suffers from depression．And that's what has scientists confused．If depression causes harm to the body，why is it so widespread in the population？Some scientists think they may have the answer．Depression may have an evolutionary （进化） benefit．It may improve one's chances of fighting off infection （感染）．
Scientists have known that depressed people show an immunoreactive （免疫反应性的） condition known as inflammation （炎症），even when they are not infected．For several years they have been finding that genes （基因） linked to depression also affect the function of the immune system．Stresses，which can lead to depression，also change the immune system．These findings suggested that depression was somehow linked to the body's ability to fight disease．
Some scientists now come up with the idea that depression might have had an evolutionary advantage in the days before modern medicine and antibiotics （抗生素）．Infection was a major cause of death in early human history．Surviving those infections determined which genes were passed to the next generation．
They doubt that depression helped people，especially children，stay alive from infection．Extreme tiredness leads to inactivity and less social contact which helps keep infection from spreading．Having no appetite helps avoid food sharing which can also spread infection．Sleeplessness，which is associated with both depression and immune system activation，may have been a mechanism to keep a person alert（机警） to fight off enemies after injury．
If scientists are correct about this link，it could lead to new treatments for depression．They are interested in drugs that treat conditions where the immune system attacks the person's own body，known as auto immune diseases．It is possible that medicine known to treat auto immune disease may be successful in treating depression also．
80．The underlined sentence in Paragraph 1meansD．
A．there is a depression line between different groups and societies
B．people at a higher social position may tend to suffer from depression
C．people who are living with depression could connect with each other
D．anyone can get depression whatever their economic states and backgrounds are
81．In Paragraph 2the authorA．
A．introduces an idea on depression
B．gives an example to show his idea
C．explains how depression works
D．describes the depression problems
82．According to the passage，which of the following is TRUE？B
A．Depression can spread infection．
B．Stress may affect the function of the immune system．
C．Women are less likely to suffer from depression．
D．Modern medicine is widely used for treating depression．
83．The writer mainly wants to tell people that depressionC．
A．is serious but highly treatable disease
B．could have its advantages in scientific research
C．may improve one's chances of fighting off infection
D．is a true medical condition like high blood pressure．
分析 抑郁症不是一种选择．更贴切地说，抑郁症是像高血压或心脏病一样真实存在的疾病．仅仅在美国就有超过一千七百万人收到抑郁症的困扰，其中女性患者是男性患者的2倍．抑郁症是不分种族和社会经济条件的．每个人都可能被抑郁症困扰，包括那些既非"疯子"也不是"弱者"的人，他们也会有严重的抑郁症，但是它的治愈率是非常高的．
感觉失落吗？你并不是一个人有这种感觉．似乎抑郁症相当普遍，但这的确是事实．每十个成年人中就又一个饱受抑郁之苦．这也是科学家们感到迷惑的．如果抑郁会对人的身体造成损害，为什么它在人类中这么普遍？一些科学家认为他们可能有答案．因为抑郁可能会使人进化．它会提高人们对抗感染的能力．
科学家已经知道抑郁的人们会体现出一种免疫反应性，即炎症，即使他们没有被感染．数年以来科学家们也发现与抑郁症关联的基因会影响人体免疫系统功能．压力会使人抑郁，同时它也会改变人体免疫系统．这些发现意味着抑郁有可能与人体对抗疾病的能力有关系．
解答 80．D．句意理解题．结合Anyone can suffer from it，and those that do are not"crazy"or"weak"．They have a serious yet highly treatable disease．可知是说任何人都会患抑郁症，跨越种族和社会经济地位．故选D．
81．A．段落理解题，结合Feeling down？You're not alone．可知是在说抑郁症的一种观点，故选A．
82．B．细节理解题．结合第三段Stresses，which can lead to depression，also change the immune system可知压力可能影响免疫系统的功能，故选B．
83．C．推理题，结合Sleeplessness，which is associated with both depression and immune system activation，may have been a mechanism to keep a person alert（机警） to fight off enemies after injury．可知抑郁症有可能会帮助抵抗感染，故选C．
点评 做本题时，首先对原文材料迅速浏览，掌握全文的主旨大意． 其次，细读题材，各个击破．掌握全文的大意之后，细细阅读每篇材料后的问题，弄清每题要求后，带着问题，再回到原文中去寻找、捕获有关信息．
