Psychological disorders can range from mild to severe. Adjustment disorder involves problems coping with stressors. Psychological disorders are classified using the DSM-IV-TR's multiaxial system, which provides diagnoses and assessments of functioning. Anxiety disorders include phobias, panic disorder, generalized anxiety disorder, obsessive-compulsive disorder, and post-traumatic stress disorder. Dissociative disorders involve changes in identity or consciousness, while somatoform disorders involve physical symptoms without medical causes. Mood disorders include major depression and bipolar disorder, which involve alternating between manic and depressive states.