431 children (233 boys, 198 girls) born in Stockholm, Sweden, had a detailed behavioral assessment at 11 years of age, including a detailed interview with their school teachers, and at age 27 years were reevaluated to identify alcoholism or alcohol abuse. Specific predictions from a neurobiological learning theory about the role of heritable personality traits in susceptibility to alcohol abuse were tested in this prospective longitudinal study. Three dimensions of childhood personality variation were identified and rated without knowledge of adult outcome. These three dimensions (novelty-seeking, harm avoidance, and reward dependence) were largely uncorrelated with one another, and each was predictive of later alcohol abuse. Absolute deviations from the mean of each of the three personality dimensions were associated with an exponential increase in the risk of later alcohol abuse. High novelty-seeking and low harm avoidance were most strongly predictive of early-onset alcohol abuse. These two childhood variables alone distinguished boys who had nearly 20-fold differences in their risk of alcohol abuse: the risk of alcohol abuse varied from 4 to 75% depending on childhood personality.

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The Nordic countries were screened for the occurrence of cases of autism with a same-sexed twin under age 25 years. Twenty-one pairs (11 monozygotic and 10 dizygotic) of twins and one set of identical triplets were found and extensively examined. The concordance for autism by pair was 91% in the monoygotic and 0% in the dizygotic pairs. The corresponding concordances for cognitive disorder were 91% and 30%, respectively. In most of the pairs discordant for autism, the autistic twin had more perinatal stress. The results lend support for the notion that autism sometimes has a hereditary component and that perinatal stress is involved in some cases.

Type 1 and type 2 alcoholism are clinically distinct forms of alcoholism with causes that are independent but not mutually exclusive.

Recent progress toward a systematic pathophysiological model of alcoholism has led to identification of two distinct subtypes of alcoholism. These subtypes may be distinguished in terms of distinct alcohol-related symptoms, personality traits, ages of onset, and patterns of inheritance. Type 1 alcoholism is characterized by anxious (passive-dependent) personality traits and rapid development of tolerance and dependence on the anti-anxiety effects of alcohol. This leads to loss of control, difficulty terminating binges once they start, guilt feelings, and liver complications following socially encouraged exposure to alcohol intake. In contrast, type 2 alcoholism is characterized by antisocial personality traits and persistent seeking of alcohol for its euphoriant effects. This leads to early onset of inability to abstain entirely, as well as fighting and arrests when drinking. Empirical findings about sex differences, ages of onset, associated personality traits, and longitudinal course are described in a series of adoption and family studies in Sweden and the United States. Implications for future research and clinical practice are discussed.