Mental Illness DSM IV (Diagnostic and Statistical Manual of Mental Disorders, fourth edition. This has no theoretical basis; that is, it is based no theory about the cause(s) of mental disorders. Presently, its main function has to do with insurance coverage.

Possible evolutionary causes of behavioral disorders Possible evolutionary causes of behavioral disorders. Why above mutational levels? Not disorders, but defenses. Side effects of genes with fitness benefits. Frequency dependent selection. Missing or malfunctioning module. Mismatch between present environment and EEA. Extremes of normal polygenic distribution.

Not disorders, but defenses. Analogy: fever. Possible psychological example: depression. Withdraw from failing strategies. Negotiate for more support.

2. Side effects of genes with fitness benefits. Analogy: sickle-cell anemia. Possible psychological examples: schizophrenia; bipolar disorder. Both heritable. Fitness benefits to (self or) other carriers of the same gene.

2a. Bipolar disorder (manic depression; severe mood swings). May be very productive during manic phases. Relatives show high intelligence and creativity.

2b. Schizophrenia; disintegration of self. Hear voices, inappropriate emotion, incoherent thoughts, experience “alien control.” Like Bipolar Disorder, relatives of schizophrenics show high intelligence and creativity. Also may be example of defective module (see below).

3. Frequency dependent selection. Analogy: “transvestite behavior” in hanging flies. Possible psychological example: sociopathy: Superficially charming and sociable but egocentric, impulsive and lacking in emotions of shame, guilt, indebtedness. Could exist at low frequency in a population of reciprocal altruists.

3. Frequency dependent selection. Analogy: “transvestite behavior” in hanging flies. Possible psychological example: sociopathy: Superficially charming and sociable but egocentric, impulsive and lacking in emotions of shame, guilt, indebtedness. Could exist at low frequency in a population of reciprocal altruists.

4. Missing or malfunctioning module. Analogy: inability to feel pain. Possible psychological example: Autism: Impaired in social interaction, poor eye contact, lack of emotional tone, delayed and repetitive language, preoccupation with objects, repetitive behaviors. Defective theory of mind module. (Why? Modular view just identifies the natural cleavage points.)

5. Mismatch between present environment and EEA. Analogy: dietary cravings that lead to obseity. Possible psychological example: Anxiety disorders. Novel dangers ->increased vigilance Many strangers Media amplification of risks

6. Extremes of normal polygenic distribution. Analogy: any polygenic trait. Possible psychological example: Clinical depression: Overly sensitive to discouragement.