The National Institute of Mental Health reports that 26.2 percent of adults suffer from a mental illness each year. Mental illness is a broad term that encompasses neuroses such as anxiety, psychoses such as schizophrenia, and personality disorders. Patients with neuroses are usually grounded in reality and have conditions that allow them to function in society. Patients with psychoses may have thoughts not based in reality or may experience psychotic episodes with periods of lucidity. Without treatment, most people with psychosis have great difficulty functioning in society.
Hallucinations
Seeing things that others don't or hearing voices that others don't are classic signs of mental illness. The person may also feel things crawling on him that are not present. He may seem to be talking to himself.
Persistent Odd Beliefs
Peculiar beliefs about others or one's self can indicate mental illness. The person may believe the government is spying on his every move, that the waitress contaminated his food and that his neighbor is an alien. He may believe he has supernatural powers or is deemed special in some way.
Uncharacteristic Mood for Circumstances
A person with mental illness may appear happy when something devastating occurs to him or laugh hysterically at a funeral. Alternatively, he may seem depressed even though his life appears to be satisfying. He may also display a lack of emotion--regardless of the circumstances--such as when someone destroys his property or he wins a monetary prize.
Self-destructive Behavior
A person with severe, persistent self-destructive behavior may suffer from a mental illness. Risk-taking, such as illegal drug abuse or dangerous criminal behavior, may reveal a serious mental condition. This person may repeatedly end up in jail or the hospital despite the consequences.
Inability to Get Along With Others
The person with mental illness may verbally or physically abuse family members, terrorize neighbors or threaten authority figures. He may have no true friends and no desire to maintain any friendships. Alternatively, he may attempt to make friends or form intimate relationships but have such a severe personality disorder that he's unable to maintain a relationship. People who enjoy being alone and lead a stable life should not be classified in this group.
Lack of Self-worth
A persistent lack of self-worth is indicative of mental illness. Though this may be a phase that many teenagers experience, expressions of self-hate or suicidal attempts are warning signs of mental illness in people of any age. In less extreme cases, the person allow others to abuse her or consistently doesn't care for her own emotional needs.
Inability to Hold a Job
The consistent inability to maintain a job may be indicative of mental illness. This could be due to anger issues, inability to follow instructions or self-sabotaging behavior, such as chronic tardiness. This person may be repeatedly fired from work or may quit numerous positions as soon as his initial attraction to the job wears off.
Inability to Follow Basic Instructions
The person with severe mental illness may be unable to comprehend or follow basic instructions. Complex thinking that's needed to drive a car to a new location or follow the instructions on a form may prove impossible to this person. People with learning disabilities shouldn't necessarily be placed in this classification.
Lack of Empathy
A complete lack of empathy can indicate mental illness. This person may not be moved by seeing a parent cry for a dying child. He may not understand empathy in others and not comprehend why his wife is upset upon hearing a friend lost her job. This lack of empathy can make him a very dangerous person. Alternatively, he may quietly conduct his life and avoid issues he doesn't understand.
Lack of Self-care
A person who doesn't properly meet his own self-care needs may suffer from a mental illness. This person may show a decline in personal hygiene or be unable to sleep at night. Mayo Clinic describes someone who may overeat or stop eating properly as possibly having a mental illness. Also in this broad classification is someone who's unable to shop for groceries or travel from place to place due to anxiety. He may avoid going to the dentist or doctor due to extreme fear.
