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Aetiology of antisocial personality and psychopathy

Aetiology of antisocial personality and psychopathy

The apparent confusion between antisocial personality and psychopathy has meant that the relevant literature often confuses the two concepts. Some studies of antisocial personality include within them what Hare and others would consider to be psychopathy. Other studies specifi cally focus on psychopathy as defi ned by Hare. As psychopathy is linked to an ‘antisocial lifestyle’, it is perhaps not surprising that many of the factors that predispose to antisocial behaviour are also associated with psychopathy. What distinguishes psychopathy from the antisocial personality are distinct neurological factors that are uniquely associated with the emotional detachment and limited range or depth of emotions central to the condition. Accordingly, this section fi rst considers factors that increase risk for antisocial behaviour or personality, before considering the neurological factors that contribute uniquely to the development of psychopathy.

Genetic factors

Genetic studies of families have found it diffi cult to discriminate between genes for problem drinking, criminality and antisocial behaviour, all of which seem to be closely related. Nevertheless, two early adoptee studies implicated genetic factors in the aetiology of antisocial behaviour. Crowe reported that adopted-away children of women prisoners with antisocial personality disorder had higher rates of antisocial personality than control adoptees without this family history. Similarly, Cadoret  found that rates of antisocial behaviour were higher among adopted adolescent females with a biological relative who engaged in antisocial behaviour than a matched group of adolescents without this family history. Risk for engaging in antisocial behaviour was further increased if the environment of the adoptive family was ‘adverse’, indicating an interaction between social and genetic factors in the development of antisocial behaviour. Two recent studies add to the evidence of this interplay between genetic and environmental infl uences. In one US study, Legrand et al. found that antisocial behaviour was substantially infl uenced by genetic factors in urban environments, By contrast, environmental factors were more infl uential in rural environments. The apparent lack of infl uence of the urban environment may refl ect the lack of variation – and universally challenging nature – of many urban environments. In a study adding strength to Hare’s distinction between antisocial personality and psychopathy, Larsson et al. found that psychopathic behaviour was largely driven by genetic factors, while the impact of genetic factors on antisocial behaviour was signifi cantly moderated by environmental factors.

Biological mechanisms

One gene that appears to be implicated in moderating risk for antisocial personality affects serotonin metabolism within the body. Not surprisingly, therefore, there is increasing evidence that high levels of impulsivity, and perhaps aggression, irritability and sensation seeking are associated with low levels of serotonin, although the issue is far from clear-cut. Dolan et al. (2002), for example, found that impulsivity appeared to be related to both frontal lobe (executive) and serotonin function. By contrast, while aggression was correlated inversely with frontal (executive) and temporal lobe (memory) function, it was not related to serotonin levels. Low levels of sympathetic activity (noradrenalin) at times of stress may also be implicated in antisocial behaviour, perhaps because they predispose the individual to fearlessness and thrill seeking as a means of increasing arousal levels.

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