Substance use disorders and other mental disorders have common risk factors. Common risk factors, including inherited characteristics, adverse social environments, trauma, and stress, can contribute to substance use and other mental disorders. For example, childhood trauma increases the risk for substance use, other mental disorders, suicidality, and physical health conditions.15,16 One analysis of existing studies estimated that over 30% of adults with substance use disorder had childhood trauma including emotional abuse, sexual abuse, emotional neglect, or physical neglect.17
Other mental disorders can contribute to substance use and to substance use disorders. Patients with mental disorders are at greater risk for substance misuse.18 There are many interrelated factors that can contribute to this. First, people who experience anxiety, stress, depression, or pain may use drugs to try to feel better, especially if they lack access to mental health care.19 Although some substances may temporarily reduce symptoms of a mental disorder, they can also make symptoms worse, both immediately and in the long run.1
Substance use problems may involve similar changes to brain circuitry as some mental disorders. For example, research suggests that attention-deficit/hyperactivity disorder (ADHD) is associated with the same brain changes as those associated with drug cravings.20,21 This may explain why patients with both substance use disorders and ADHD often report greater drug cravings.22,23,24
Substance use can contribute to the development of mental disorders and make them worse. Substance use can lead to changes in some of the same brain areas that are disrupted in other mental disorders, such as schizophrenia, anxiety, mood, or impulse-control disorders.2 For example, evidence suggests that cocaine use may worsen the symptoms of bipolar disorder and contribute to progression of this illness).25 Some evidence has linked cannabis use to earlier onset of psychosis in people with genetic risk factors for psychotic disorders, including schizophrenia, as well as worse symptoms in people who already have these conditions.26