If you have a mental illness and substance abuse issues at the same time then a dual diagnosis is needed so that you can start the long road to recovery and avoid any setbacks or relapses. Substance abuse and mental illness that coexist can be like the chicken and the egg joke, and without a full diagnostic evaluation and work up an accurate diagnosis can not be reached and an effective treatment plan can not be developed.
Sometimes mental illness is caused by substance abuse, but in other cases this is reversed. Some individuals may use drugs or alcohol to try and minimize or eliminate symptoms of mental illness. Individuals with schizophrenia and bipolar disorder have reported using drugs or alcohol to stop voices or control episodes of mania or depression. This self medication only complicates the situation, and all disorders must be treated at the same time for the best possible results. If one problem is treated but the other is ignored then any treatment can provide short term results at the most, and no improvement may be seen because only one of the disorders is being treated. This is a common mistake, and often a person will get help for mental health problems or seek substance abuse treatment without doing both simultaneously.