A key distinction between these methods of reasoning is the role of volition. That is, symptoms of psychiatric diseases – memory disturbance, hallucinations, and emotional disturbance – are typically understood as arising involuntarily. In contrast, behavioral disorders centrally involve voluntary control (though undoubtedly persons do not choose behavioral disorders). “Common sense” might suggest that neurobiological and genetic factors should be especially influential in the genesis of psychiatric syndromes that are disease-like in their manifestations, while other forces might have greater impact on the genesis of syndromes that manifest with disturbed behaviors. That is, common sense might suggest that any syndromes that centrally involve human decision making (Do I take this next drink? Do I eat this donut?) should be less genetically influenced than syndromes in which symptoms appear unbidden. Such reasoning is consistent with the public’s notion that behavioral disorders like alcoholism are more “self-inflicted” than schizophrenia, depression, or Alzheimer’s Disease (Schomerus et al., 2006).
