The common liabilities model in psychology proposes that there is a shared genetic vulnerability or predisposition for various externalizing disorders, such as attention deficit hyperactivity disorder (ADHD), conduct disorder (CD), oppositional defiant disorder (ODD), and substance use disorders. This model suggests that these disorders co-occur frequently because they share a common underlying genetic liability.
One of the key concepts in the common liabilities model is behavioral disinhibition (BD). BD refers to a tendency towards impulsive, aggressive, and inattentive behaviors, as well as low persistence and self-control. These traits are believed to reflect a common genetic vulnerability that predisposes individuals to various externalizing disorders.
The idea of a common liability is supported by research that has consistently found high rates of comorbidity among externalizing disorders. For example, individuals with ADHD often also meet criteria for CD or ODD, and those with CD or ODD are at increased risk for developing substance use disorders later in life.
The common liabilities model suggests that rather than each disorder having its own distinct genetic basis, there is likely a shared set of genetic factors that contribute to the development of multiple externalizing disorders. These genetic factors may interact with environmental influences and individual characteristics to increase the risk for specific disorders.
It is important to note that the common liabilities model does not suggest that all individuals with BD will develop externalizing disorders. Instead, it posits that individuals with a higher degree of BD are more likely to develop these disorders, compared to those with lower levels of BD.
Personal experiences and situations can provide insight into the common liabilities model. For example, imagine a person who has always struggled with impulsivity, inattention, and difficulty controlling their aggressive tendencies. This individual may have been diagnosed with ADHD as a child, but as they grew older, they also developed conduct problems and engaged in substance use. This real-life scenario aligns with the common liabilities model, as it suggests that the individual's genetic vulnerability towards BD predisposed them to develop multiple externalizing disorders.
The common liabilities model proposes that the high comorbidity among externalizing disorders is due to a shared genetic vulnerability for traits and behaviors associated with behavioral disinhibition. This model suggests that understanding the common underlying genetic factors can help us better understand and potentially intervene in the development and treatment of externalizing disorders.