By Sonia Tagliareni of DrugRehab.com #Fearless Family Writer Mental illness and substance use disorders go hand in hand. People struggling with drug use disorders are twice as likely as the general population to struggle with mood and anxiety disorders, according to the National Institute on Drug Abuse. The 2014 National Survey on Drug Use and Health reported that 7.9 million Americans suffered from a co-occurring mental illness and substance use disorder. People suffering from depression, anxiety disorders, schizophrenia and personality disorders are more likely to experience addiction, according to MentalHealth.gov. Substance use disorders and mental health disorders share similar risk factors, including: Genetic risk factors that make a person vulnerable to substance use and mental health disorders Environmental risk factors, such as stress, trauma and early exposure to drugs They also have similar traits, such as: The ability to change similar parts of the brain The ability to disrupt development, especially during early childhood People who use drugs may experience symptoms of mental illness. For example, people who abuse marijuana are at an increased risk of …