Mental illnesses are health conditions involving changes in emotional, thinking, or behavioral patterns. The most common forms of mental disorders are neurodevelopmental disorders, obsessive-compulsive disorder, bipolar disorder, and schizophrenia. Factors such as a traumatic brain injury, use of alcohol and recreational drugs and chemical imbalances in brain can lead to the development of mental disorders. There are several signs and symptoms of mental disorders such an inability to cope with daily problems or stress, suicidal thinking, major changes in eating habits, fatigue, low energy, and sleeping problems. Patients with mental health disorders can be best managed with the help of a mental health treatment plan or mental health care plan, which involves three basic steps, namely, assessment, planning, and referral. The assessment step involves assessing a patient's mental health condition and making a diagnosis. Planning includes preparing a mental health treatment plan. The last step, referral, involves referring a patient to psychologist, psychiatrist, or other occupational therapists. This book addresses the treatment and interventions for mental health disorders. It will help new researchers by foregrounding their knowledge in this branch.