Common symptoms of depression include persistent sadness, loss of interest in activities, changes in appetite or sleep patterns, fatigue, difficulty concentrating, feelings of worthlessness, and social withdrawal.

Common symptoms of bipolar disorder include alternating periods of intense mania—characterized by elevated mood, increased energy, and impulsivity—and episodes of depression, marked by persistent sadness, fatigue, and loss of interest in activities.

Common symptoms of Post-Traumatic Stress Disorder (PTSD) include intrusive memories of the traumatic event, avoidance of reminders of the trauma, negative changes in mood and cognition, and heightened arousal, such as increased anxiety or irritability.

Common symptoms of eating disorders include extreme preoccupation with food, body weight, and shape; significant fluctuations in weight; restrictive eating or bingeing; purging behaviors; and emotional distress related to eating habits and body image.

Common symptoms of addiction and substance use disorders include a strong craving for the substance, loss of control over its use, continued use despite negative consequences, tolerance (requiring more of the substance to achieve the same effect), and withdrawal symptoms when not using the substance.