The term comorbidity refers to the simultaneous presence of two (or more) illnesses or disorders in the same individual. Mental illness and substance abuse frequently co-occur in this manner. According to the National Institute on Drug Abuse, six out of ten people with a substance use disorder also suffer from another form of mental illness, such as an anxiety disorder ("Comorbidity," NIDA). Data from the National Comorbidity Survey reveal those who suffer from an anxiety disorder are 2-3 times more likely than the general population to experience a substance use disorder at some point in their lives (Kessler et al, "Lifetime and 12-Month Prevalence").
The reasons behind the high rate of this comorbidity are numerous and complex. One disorder does not invariably lead to the other, nor is one always the cause or result of the other. A substance abuse disorder may develop from the attempt to mask or numb anxiety symptoms with drugs or alcohol. Or, an anxiety disorder may develop from the physical, social or legal consequences of substance abuse.
There are several theories as to why anxiety disorders and substance abuse so commonly go hand-in-hand. In any given instance, one or more of these factors may play a part in their simultaneous manifestation:
Common genetic predisposition. Emerging evidence suggests that similar genetic factors may predispose individuals to both addiction and mental disorders or to having a greater risk of the second condition once the first develops.
Similar environmental triggers. Trauma, stress and early exposure to drugs are common factors that can lead to both substance abuse and mental illness, particularly in individuals with underlying genetic vulnerabilities.
Interaction with similar brain regions. Certain parts of the brain are impacted by both drug abuse and mental illness. For example, brain circuits linked to reward processing and those involved in the stress response are both impaired by substance abuse and show abnormalities in particular mental disorders.
Role as developmental disorders. Drug abuse and mental illness often emerge during adolescence or childhood, when the brain is undergoing dramatic developmental changes. Early exposure to drugs can affect the brain in ways that increase the risk for mental illness, just as early symptoms of a mental disorder may increase vulnerability to drug abuse.
Most people with alcohol or substance abuse and an anxiety disorder experience them independently, but having both can create a vicious cycle. This form of comorbidity creates a bi-directional interaction that is interdependent and self-feeding. For example,
depressants such as alcohol and
opiates may be used in an attempt to decrease anxiety, but during withdrawal states, anxiety is increased. This leads to an exacerbation of the anxiety disorder, making relapse to substance use more likely (Brady).
Go To Chicken & Egg: Self-Medication and Substance-Induced Anxiety