Abnormal Psychology

Mood Disorders and Suicide 203

However, genes are not destiny. The environment clearly plays an important

role in whether a person will develop depression (Eley et al., 1998; Hasler et al.,

2004; Rice, Harold, & Thaper, 2002; Wender et al., 1986). Even with identical

twins, if one twin is depressed, this does not guarantee that the co-twin will also be

depressed—in spite of their having basically the same genes. Whether a person gets

depressed depends partly on his or her life experiences, including the presence of

hardships and the extent of social support.

The environment plays a key role not only in whether the genes contribute to

depression, but also in how the genes have their effects. In some cases, genetic fac-

tors may affect depression indirectly—by disrupting specifi c aspects of normal func-

tioning that in turn trigger the disorder. For example, researchers have found that

genetics may infl uence whether a person has disrupted sleep (Hasler et al., 2004;

Modell et al., 2003), and adolescents who went on to develop the disorder (investi-

gated in longitudinal studies) did have disrupted sleep.

Psychological Factors

Particular ways that people think about themselves and events, in concert with

stressful or negative life experiences, can increase the risk of depression. In the fol-

lowing sections we consider psychological factors that can infl uence whether a per-

son develops depression; these factors range from biases in attention to the effects

of different ways of thinking to the results of learning.

Attentional Biases

Some people see a glass that is half full of water as being half empty. Similarly, some

people focus their attention—consciously or unconsciously—on stimuli that are sad.

People who are depressed are more likely to pay attention to sad and angry faces

than to faces that display positive emotions (Gotlib, Kasch, et al., 2004; Gotlib,

Krasnoperova, et al., 2004; Leyman et al., 2007); people who do not have a psy-

chological disorder spend equal time looking at faces that express different emo-

tions. This attentional bias has also been found for negative words and scenes, as

well as for remembering depression-related—versus neutral—stimuli (Caseras et al.,

2007; Gotlib, Kasch, et al., 2004; Matt, Vasquez, & Campbell, 1992; Mogg, Brad-

ley, & Williams, 1995). Such an attentional bias may leave depressed people more

sensitive to other people’s sad moods and to negative feedback from others (or

even a lack of positive feedback, as occurs when a person fails to smile when

greeting you), compounding their depressive thoughts and feelings.

Dysfunctional Thoughts

As discussed in Chapter 2, Aaron Beck proposed that cognitive distortions are the

root cause of many disorders. Beck (1967) has suggested that people with depres-

sion tend to have overly negative views about (1) the world, (2) the self, and (3) the

future, referred to as the negative triad of depression. These distorted views can

cause and maintain chronically depressed feelings and depression-related behaviors.

For instance, a man who doesn’t get the big raise he hoped for might respond with

cognitive distortions that give rise to dysfunctional thoughts. He might think that

he isn’t “successful” because he didn’t get the raise, and therefore that he must be

worthless (notice the circular reasoning). This man is more likely to become de-

pressed than he would be if he didn’t have such dysfunctional thoughts.

Rumination

While experiencing negative emotions, some people refl ect on these emotions; dur-

ing such ruminations, they might say to themselves: “Why do bad things always

happen to me?” or “Why did they say those hurtful things about me—is it something

I did?” or “Should I have spoken more during the discussion?” (Nolen-Hoeksema &

Morrow, 1991). Such ruminative thinking has been linked to depression (Just &

Alloy, 1997; Nolen-Hoeksema, 2000; Nolen-Hoeksema & Morrow, 1991, 1993).

Studies have examined the relationship between depression and specifi c forms of

rumination, such as stress-reactive rumination, which is ruminating about negative

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