section_path: Risk factors/Comorbid disorders
section_name: Comorbid disorders
paragraph_text: Comorbid disorders
  
  Individuals with comorbid (i.e., co-occurring) mental health disorders such as depression, anxiety, attention-deficit/hyperactivity disorder (ADHD) or post-traumatic stress disorder are more likely to develop substance use disorders. The NIDA cites early aggressive behavior as a risk factor for substance use. The National Bureau of Economic Research found that there is a "definite connection between mental illness and the use of addictive substances" and a majority of mental health patients participate in the use of these substances: 38% alcohol, 44% cocaine, and 40% cigarettes.