The most common psychological problems include depressive disorder, bipolar disorder, hypochondria, sleep disorders, addictions, and low self-esteem. Depressive disorder is characterized by depressed mood, loss of interest, negative thinking, and thoughts of death or suicide. Bipolar disorder involves mood swings between mania and depression. Hypochondria is an irrational fear of illness. Sleep disorders negatively impact daily life if persistent. Addictions are characterized by a desire to continue taking a substance and withdrawal symptoms when use stops. Low self-esteem involves constant self-criticism and negative self-evaluations.