Abnormal Psychology

200 CHAPTER 6

Brain Systems

Studies of depressed people have shown that they have unusually low activity

in a part of the frontal lobe that has direct connections to the amygdala (which

is involved in fear and other strong emotions) and to other brain areas involved

in emotion (Kennedy et al., 1997). This fi nding hints that the depressed brain is

not as able as the normal brain to regulate emotion. Moreover, this part of the

frontal lobe has connections to the brain areas that produce the neurotransmitter

substances dopamine, serotonin, and norepinephrine. Thus, this part of the fron-

tal lobe may well be involved in regulating the amounts of such substances. This

is important because these substances are involved in reward and emotion, which

again hints that the brains of these people are not regulating emotion normally.

Researchers have refi ned this general observation and reported that one aspect of

depression—lack of motivated behavior—is specifi cally related to reduced activity in

the frontal (and parietal) lobes (Milak et al., 2005). In addition, these researchers re-

port that depression does not simply refl ect that the brain as a whole has become slug-

gish. Rather, they found that more severe depression is associated with greater activity

in the emotion-related limbic system, which fi ts with the idea that emotions are not

being effectively regulated. Moreover, these researchers found that some of the brain

areas involved in attention (in particular, the thalamus) and in controlling movements

(basal ganglia) are overactive in depressed people, which again suggests that the

functions carried out by these brain areas are not being regulated normally.

Neural Communication

Researchers have long known that the symptoms of depression can be alleviated

by medications that alter the activity of serotonin or norepinephrine (Arana &

Rosenbaum, 2000). Indeed, when this fact was fi rst discovered, some researchers

Table 6.5 • Dysthymic Disorder Facts at a Glance

Prevalence

• In a given year, 3% of Americans have dysthmic disorder; 6% will have it over the course of
  their lives.

Comorbidity

• Among individuals with dysthymic disorder without a prior history of MDD, the risk of subse-
  quently developing MDD is approximately 75% within 5 years of the onset of dysthymia.


• People with dysthymic disorder may also develop a substance-related disorder.

Onset

• The onset of dysthymia tends to be earlier than that of MDD.

Course

• The spontaneous remission rate (that is, the rate at which the disorder gets better by itself,
  without any treatment) for people with dysthymic disorder is only 10% per year.


• In one 10-year study, almost 75% of people with dysthymic disorder recovered within 5 years,
  but over 70% of the patients who recovered had a recurrence by the end of the study (Klein,
  Shankman, & Rose, 2006).


• Each year, approximately 10% of individuals with dysthymic disorder will have their fi rst MDE.


• People whose dysthymic disorder precedes the onset of MDD, as occurs for 10–25% of people
  with MDD, are less likely to have a full recovery between episodes without treatment.

Gender Differences

• Boys and girls are equally likely to develop dysthymic disorder.


• In adulthood, women are two to three times more likely than men to develop dysthymic disorder.
  Source: Unless otherwise noted, the source for information is American Psychiatric Association, 2000.