Sometimes people confuse three mental disorders, only one of which could be referred to as “common” within the population — bipolar disorder (also known as manic-depression), schizophrenia, and multiple personality disorder (also known by its clinical name, dissociative identity disorder). This confusion has largely resulted from the common use of some of these names in popular media, and as short-hand by people referring to someone who is grappling with a mental health issue. The disorders, however, have little in common other than the fact that many who have them are still stigmatized by society.

Bipolar Disorder

Bipolar disorder is a fairly common mental disorder compared with the other two disorders. Bipolar disorder is also well-understood and readily treated by a combination of medications and psychotherapy. It is characterized by alternating moods of mania and depression, both of which usually last weeks or even months in most people who have the disorder. People who are manic have a high energy level and often irrational beliefs about the amount of work they can accomplish in a short amount of time. They sometimes take on a million different projects at once and finish none of them. Some people with mania talk at a faster rate and seem to the people around them to be constantly in motion.

After a manic mood, a person with bipolar disorder will often “crash” into a depressive mood, which is characterized by sadness, lethargy, and by a feeling that there’s not much point in doing anything. Problems with sleep occur during both types of mood. Bipolar disorder affects both men and women equally and can be first diagnosed throughout a person’s life.

Bipolar disorder can be challenging to treat because, while a person will take an antidepressant medication to help alleviate a depressed mood, they are less likely to remain on the medications which help rein in the manic mood. Those medications tend to make a person feel “like a zombie” or “emotionless,” which are feelings most people wouldn’t want to experience. So many people with bipolar disorder find it difficult to maintain treatment while in their manic phase. However, most people with bipolar disorder function relatively well in normal society and manage to cope with their mood swings, even if they don’t always keep on their prescribed medications.

For more information about bipolar disorder, please see our Bipolar Guide.


Schizophrenia is less common than bipolar disorder and is usually first diagnosed in a person’s late teens or early to late 20’s. More men than women receive a diagnosis of schizophrenia, which is characterized by having both hallucinations and delusions. Hallucinations are seeing or hearing things that aren’t there. Delusions are the belief in something that isn’t true. People who have delusions will continue with their delusions even when shown evidence that contradicts the delusion. That’s because, like hallucinations, delusions are “irrational” — the opposite of logic and reason. Since reason doesn’t apply to someone who has a schizophrenic delusion, arguing with it logically gets a person nowhere.

Schizophrenia is also challenging to treat mainly because people with this disorder don’t function as well in society and have difficulty maintaining the treatment regimen. Such treatment usually involves medications and psychotherapy, but can also involve a day program for people who have more severe or treatment-resistant forms of the disorder.

Because of the nature of the symptoms of schizophrenia, people with this disorder often find it difficult to interact with others, and conduct normal life activities, such as holding down a job. Many people with schizophrenia go off of treatment (sometimes, for instance, because a hallucination may tell them to do so), and end up homeless.

For more information about Schizophrenia, please see our Schizophrenia Guide.

Multiple Personality Disorder (Dissociative Identity Disorder)

This disorder used to be known as multiple personality disorder (and is still commonly referred to as such in the media), but is now known by its newer clinical name, dissociative identity disorder (DID). DID is characterized by a set of one or more distinct identities that a person believes to exist within themselves. These identities can talk to the person, and the person can answer back. The identities often are formed to help a person cope with different parts of their life, and seem to have distinct personalities that are unique and different than the person’s core personality.

Sometimes, people with DID will lose track of time or will be unable to account for blocks of time during their day. This occurs when one of the identities within the person takes control of the individual and engages in behaviors that the core personality would otherwise not engage in. For instance, the person with DID may be unable to be assertive in a situation with her boss, so the assertive identity takes over for the important meeting to ensure the individual is assertive.

Dissociative identity disorder is not commonly diagnosed within the population, and is not well understood by mental health professionals and researchers. Treatment typically involves psychotherapy to help integrate all of the identities into the core personality and can take years when successful.

For more information about Multiple Personality Disorders, please see our Multiple Personality Disorder Guide.

Contrasting the Three Very Different Disorders

People with bipolar disorder usually can lead fairly “normal” lives, hold down a regular job, have a happy relationship and family, even be very successful in a career. People with bipolar disorder do not hear voices that aren’t there, and they do not have multiple personalities in their bodies. People with bipolar disorder do best when they stick to some treatment regimen.

Many people with schizophrenia often have a more difficult time functioning in normal society. Because of the nature of the disorder, people with schizophrenia often have a hard time staying in treatment, and an even harder time with social relationships, family, friends, and work. Still one of the most stigmatized disorders in mental health, help in many communities can be hard to come by and many people with schizophrenia end up homeless and forgotten by their family and society.

People with schizophrenia who have strong community and family support and resources do well, and can lead happy, healthy, fulfilling lives, with rewarding family and social relationships. People with schizophrenia can be depressed or manic, but it is usually as a result of the schizophrenia itself (e.g. they are depressed because they have schizophrenia). If a person hears voices (not all people with schizophrenia do), they do not recognize the voices as being a part of themselves.

People with multiple personality disorder, or dissociative identity disorder (DID), can often lead successful, “normal” lives with healthy, happy relationships with others. While, like people with schizophrenia, they can “hear voices” in their head, the voices are recognized by the person as different identities within themselves (not as external voices from outside themselves). Such identities may help the person function in life, and may allow the person to live their lives with only disruption. Others with DID have a more difficult time, because the identities take over parts of their life, making accounting for time throughout the day challenging and frustrating. While a person may become depressed with DID, it is secondary to the DID symptoms themselves (e.g., the person is depressed because they are trying to cope with their DID).

People seem to most often confuse someone who is suffering from schizophrenia with someone who has dissociative identity disorder. While both are chronic, serious mental health concerns, the differences between these two disorders are stark. People with schizophrenia hear or see things that aren’t there and believe things that aren’t true, often tied into a complex, irrational belief system. They do not have multiple identities or personalities. People with DID do not have delusion beliefs, outside of their multiple personalities or identities. The only voices they hear or talk to are these identities.