The co-occurrence of two conditions may also come about due to the presence of shared biological, psychological, social, or environmental risk factors. That is, the factors that increase the risk of one condition may also increase the risk for another [38, 44-47]. For example, both AOD and mental health conditions have been associated with lower socioeconomic status, cognitive impairment, the presence of conduct disorder in childhood and antisocial personality disorder (ASPD). It is also possible that a genetic vulnerability to one disorder may increase the risk of developing another disorder [47-49].
Figure 2: Explaining comorbidity