Endometriosis can cause depression, but non-directly. Because of the societal issues like doctors and other not believing the pain, limited treatment options, diagnosis by surgery, and often late diagnoses, this can create issues with the person with the disease. It can cause mental illness because of the "side-effects" of the disease. It can also exacerbate already existing mental illnesses. Because of the common feeling of being alone and the pain, it can cause suicidal thoughts as well as other mental illnesses. Any chronic illness will often have increased mental illnesses, but endometriosis can cause other problems that can cause mental illnesses as well.