Research has shown that there is a strong association between mental health disorders and substance use disorders, but findings about the order of onset and direction of influence vary by substance and type of disorder. There is strong evidence, for example, that alcohol abuse can be a contributing factor to the development of depression, but more typically the mental condition occurs prior to the substance use disorder. Associations also exist between mental disorders and substance use behaviors that do not meet the criteria for substance use disorders. For example, research suggests that adults and adolescents with major depressive episode (MDE) in the past year were more likely than those without MDE to have used alcohol heavily or to have used an illicit drug in the past year.