Here are three final ideas that may help you organize your thoughts as you reflect on what you have read in this chapter:
1. The multiple causes of mental disorders By this time in your study of psychology, you are no doubt used to the idea that human feelings, thoughts, and actions emerge from the interplay of many causes. This idea also applies to the feelings, thoughts, and actions that lead to the diagnosis of a mental disorder. The differences among us that are considered disorders—no less than the differences that are considered normal—are caused by differences in our genes and in our past and present environments. Any claim to have found the cause of generalized anxiety, depression, schizophrenia, or another major class of disorder is of doubtful validity.
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One way to review this chapter would be to think about each disorder in relation to the three classes of causes—predisposing, precipitating, and perpetuating—that were introduced near the beginning of the chapter. How might genes and early physical assaults on the brain operate through the person’s physiology to predispose him or her for the disorder? How might learned ways of thinking or acting predispose a person for the disorder? How might specific stressful events in life interact with the predisposition to precipitate the disorder? How might the disordered behavior itself, or people’s reactions to it, help perpetuate the disorder once it begins? For each disorder, think about the relationship between the research or ideas described and the possible answers to these questions. Note, too, that similar stressful events can result in different kinds of symptoms—and different diagnosed disorders—for different individuals or at different times for any given individual.
2. The continuum between normality and abnormality Although a diagnosis of a mental disorder is categorical (all or none), the symptoms on which diagnoses are made are not; they vary in degree throughout the population. Thus, any decision as to whether a particular person does or does not have a mental disorder is based on arbitrary criteria describing how severe or prolonged each symptom must be in order to call the syndrome a disorder.
As you review each disorder described in the chapter, think about its symptoms in relation to the moods, emotions, thoughts, and behaviors that all of us manifest to some degree. Doing so helps remove some of the mystique from the concept of mental disorder and helps us identify with people whose troubles are like ours, only stronger. Thinking of disorders in terms of extremes of normal processes has also helped scientists understand them better. For example, in this chapter you read about evidence relating (a) the symptoms of ADHD to normal childhood impulsiveness and exuberance; (b) the symptoms of general anxiety disorder, phobias, and obsessive-compulsive disorders to normal worries, fears, thoughts, and actions; (c) the symptoms of depression to normal, possibly adaptive mood changes following loss or failure; and (d) the auditory hallucinations experienced in schizophrenia to the intrusive thoughts that all of us experience at times.
3. An evolutionary view of mental disorder The evolutionary theme running through this book maintains that behavior is generally functional: It promotes survival and reproduction. But mental disorder is dysfunctional: It reduces one’s ability to work and interact with others effectively in survival-promoting ways. Why, then, do mental disorders exist?
One partial answer may be that mental disorders are a cost the species pays for the general advantages that come with diversity. The previous chapter, on personality, dealt with individual differences within the range generally considered healthy, or not disordered, and the case was made that natural selection may have favored diversity because those who are different from average can exploit unfilled niches and reap their rewards. Such diversity stems from variations in genes and from behavioral mechanisms that are capable of being modified through experience. Variation in capacity for anxiety, or compulsiveness, or sadness may be beneficial within a certain range; but the coin tosses that distribute genes and experiences will sometimes produce those characteristics at pathological levels.