Schizophrenia is a serious mental illness that interferes with a person’s ability to think clearly, manage emotions, make decisions and relate to others. It is a complex, long-term medical illness, affecting about 1% of Americans. Although schizophrenia can occur at any age, the average age of onset tends to be in the late teens to the early 20s for men, and the late 20s to early 30s for women. It is uncommon for schizophrenia to be diagnosed in a person younger than 12 or older than 40. It is possible to live well with schizophrenia.


It can be difficult to diagnose schizophrenia in teens. This is because the first signs can include a change of friends, a drop in grades, sleep problems, and irritability—common and nonspecific adolescent behavior. Other factors include isolating oneself and withdrawing from others, an increase in unusual thoughts and suspicions, and a family history of psychosis. In young people who develop schizophrenia, this stage of the disorder is called the "prodromal" period.

With any condition, it's essential to get a comprehensive medical evaluation in order to obtain the best diagnosis. For a diagnosis of schizophrenia, some of the following symptoms are present in the context of reduced functioning for a least 6 months:

Hallucinations. These include a person hearing voices, seeing things, or smelling things others can’t perceive. The hallucination is very real to the person experiencing it, and it may be very confusing for a loved one to witness. The voices in the hallucination can be critical or threatening. Voices may involve people that are known or unknown to the person hearing them.

Delusions. These are false beliefs that don’t change even when the person who holds them is presented with new ideas or facts. People who have delusions often also have problems concentrating, confused thinking, or the sense that their thoughts are blocked.

Negative symptoms are ones that diminish a person’s abilities. Negative symptoms often include being emotionally flat or speaking in a dull, disconnected way. People with the negative symptoms may be unable to start or follow through with activities, show little interest in life, or sustain relationships. Negative symptoms are sometimes confused with clinical depression.

Cognitive issues/disorganized thinking. People with the cognitive symptoms of schizophrenia often struggle to remember things, organize their thoughts or complete tasks. Commonly, people with schizophrenia have anosognosia or “lack of insight.” This means the person is unaware that he has the illness, which can make treating or working with him much more challenging.


Research suggests that schizophrenia may have several possible causes:

  • Genetics. Schizophrenia isn’t caused by just one genetic variation, but a complex interplay of genetics and environmental influences. While schizophrenia occurs in 1% of the general population, having a history of family psychosis greatly increases the risk. Schizophrenia occurs at roughly 10% of people who have a first-degree relative with the disorder, such as a parent or sibling. The highest risk occurs when an identical twin is diagnosed with schizophrenia. The unaffected twin has a roughly 50% chance of developing the disorder.
  • Environment. Exposure to viruses or malnutrition before birth, particularly in the first and second trimesters has been shown to increase the risk of schizophrenia. Inflammation or autoimmune diseases can also lead to increased immune system
  • Brain chemistry. Problems with certain brain chemicals, including neurotransmitters called dopamine and glutamate, may contribute to schizophrenia. Neurotransmitters allow brain cells to communicate with each other. Networks of neurons are likely involved as well.
  • Substance use. Some studies have suggested that taking mind-altering drugs during teen years and young adulthood can increase the risk of schizophrenia. A growing body of evidence indicates that smoking marijuana increases the risk of psychotic incidents and the risk of ongoing psychotic experiences. The younger and more frequent the use, the greater the risk. Another study has found that smoking marijuana led to earlier onset of schizophrenia and often preceded the manifestation of the illness.


Diagnosing schizophrenia is not easy. Sometimes using drugs, such as methamphetamines or LSD, can cause a person to have schizophrenia-like symptoms. The difficulty of diagnosing this illness is compounded by the fact that many people who are diagnosed do not believe they have it. Lack of awareness is a common symptom of people diagnosed with schizophrenia and greatly complicates treatment.

While there is no single physical or lab test that can diagnosis schizophrenia, a health care provider who evaluates the symptoms and the course of a person's illness over six months can help ensure a correct diagnosis. The health care provider must rule out other factors such as brain tumors, possible medical conditions and other psychiatric diagnoses, such as bipolar disorder.

To be diagnosed with schizophrenia, a person must have two or more of the following symptoms occurring persistently in the context of reduced functioning:

  • Delusions
  • Hallucinations
  • Disorganized speech
  • Disorganized or catatonic behavior
  • Negative symptoms

Delusions or hallucinations alone can often be enough to lead to a diagnosis of schizophrenia. Identifying it as early as possible greatly improves a person’s chances of managing the illness, reducing psychotic episodes, and recovering. People who receive good care during their first psychotic episode are admitted to the hospital less often, and may require less time to control symptoms than those who don’t receive immediate help. The literature on the role of medicines early in treatment is evolving, but we do know that psychotherapy is essential.

People can describe symptoms in a variety of ways. How a person describes symptoms often depends on the cultural lens she is looking through. African Americans and Latinos are more likely to be misdiagnosed, probably due to differing cultural or religious beliefs or language barriers. Any person who has been diagnosed with schizophrenia should try to work with a health care professional that understands his or her cultural background and shares the same expectations for treatment.


There is no cure for schizophrenia, but it can be treated and managed in several ways.

Related Conditions

People with schizophrenia may have additional illnesses. These may include:

Successfully treating schizohprenia almost always improves these related illnesses. And successful treatment of substance abuse, PTSD or OCD usually improves the symptoms of schizophrenia.