Mental illness is any disease or condition affecting the brain that influences the way a person thinks, feels, behaves and/or relates to others and to his or her surroundings. Although the symptoms of mental illness can range from mild to severe and are different depending on the type of mental illness, a person with an untreated mental illness often is unable to cope with life's daily routines and demands.

The term "mental illness" actually encompasses numerous psychiatric disorders, and just like illnesses that affect other parts of the body, they can vary in severity. As the term “mental illness” has acquired a pejorative connotation for many people, it is better to use the term “psychiatric illness/disorder”

Diagnostic and Statistical Manual – IV (DSM-IV) has categorized the disorder in the following categories.

o Anxiety Disorder
o Adjustment Disorder
o Eating Disorder
o Personality Disorder
o Mood Disorder
o Somatoform Disorder
o Psychotic Disorder
o Dissociative Disorder
o Sexual Disorder
o Impulse-Control Disorder
o Sleep Disorder

Mental Disorders are categorized according to their predominant features. This broad categorization encompasses a range of disorders. For e.g.,

o Anxiety Disorder includes
o Acute Stress Disorder
o Agoraphobia
o Generalized Anxiety Disorder [GAD]
o Obsessive-Compulsive Disorder [OCD]
o Panic Disorder (with or without Agoraphobia)
o Phobias (including Social Phobia)
o Post-Traumatic Stress Disorder [PTSD]

There are over 300 different psychiatric disorders listed in the DSM-IV. With continued research, more are named every year and some disorders are removed or re-categorized. It covers all mental health disorders for both children and adults.

Childhood disorders, often labeled as developmental disorders or learning disorders, most often occur and are diagnosed when the child is of school-age. Although some adults may also relate to some of the symptoms of these disorders, typically the disorder's symptoms need to have first appeared at some point in the person's childhood.

Based on symptoms and treatments, the disorders are broadly classified as adult, childhood, and personality disorders; some disorders may fall under more than one category.

Mental disorders can arise from a combination of sources. In many cases there is no single accepted or consistent cause currently established. A common belief even to this day is that disorders result from genetic vulnerabilities exposed by environmental stressors. However, it is clear enough from a simple statistical analysis across the whole spectrum of mental health disorders at least in western cultures that there is a strong relationship between the various forms of severe and complex mental disorder in adulthood and the abuse (physical, sexual or emotional) or neglect of children during the developmental years. Child sexual abuse alone plays a significant role in the causation of a significant percentage of all mental disorders in adult females, most notable examples being eating disorders and borderline personality disorder.

Studies have indicated that genes often play an important role in the development of mental disorders. Social influences have been found to be important, including abuse, bullying and other negative or stressful life experiences.

Diagnoses are made by psychiatrists or clinical psychologists using various methods, often relying on observation and questioning in interviews. Treatments are provided by various mental health professionals. Psychotherapy, Psychiatric medication, social interventions, peer support and self-help are the widely used methods for treatment.

Electroconvulsive therapy (ECT) is sometimes used in severe cases when other interventions for severe intractable depression have failed. Psychosurgery is considered experimental but is advocated by certain neurologists in certain rare cases.

Counseling (professional) and co-counseling (between peers) may be used. Psycho-education programs may provide people with the information to understand and manage their problems. Creative therapies are sometimes used, including music therapy, art therapy or drama therapy. Lifestyle adjustments and supportive measures are often used, including peer support, self-help groups for mental health and supported housing or supported employment (including social firms). Some advocate dietary supplements.

Psychiatric Medication is one of the major options. They include Antidepressants, Anxiolytics, Mood stabilizers, Antipsychotics and Stimulants.

World-wide more than one in three people in most countries report sufficient criteria for at least one mental illness at some point in their life. Women are found to have twice the rate of depression than men. Each year 73 million women are afflicted with major depression, and suicide is ranked 7th as the cause of death for women between the ages of 20-59.

Approximately 7% of a preschool pediatric sample was given a psychiatric diagnosis in one clinical study, and approximately 10% of 1 and 2 year olds receiving developmental screening have been assessed as having significant emotional/behavioral problems based on parent and pediatrician reports.