Anyone who's ever been to see a therapist knows Hollywood often glamorizes the experience of mental illness. Movies with mentally ill characters are often seen as Oscar-bait and can sometimes be guilty of using mental illness as a plot device. In real life, there are no miracle therapy breakthroughs that suddenly cure dissociative identity disorder. After struggling for years, no one's depression is lifted just because they finally meet that special someone that brings meaning to their life.
Mentally ill characters in movies who get better through willpower are just one trope used by Hollywood. Others include using mentally ill characters as magic beings who become savior-figures forcing change upon the hero; actually being a genius in some respect; or, existing for comedic purposes in a film. All of these tropes are dangerous in that they make light of a serious subject and look at mental illness through a romanticized filter.
Mental illness is a real experience and when Hollywood exploits it through movies that handle mental illness badly, people are then misinformed about its reality. Don't let these movies fool you.
Jim Carrey's Charlie/Hank has a mashup of dissociative identity disorder and schizophrenia which turns him into a Jekyll and Hyde-like connoisseur of poop and boob jokes. Mental health professionals loudly criticized the film for poking fun at serious mental illness, claiming schizophrenia and dissociative identity disorder were the same thing, and promoting the false image that people with schizophrenia are wild and violent.
In reality, schizophrenia does not include the possession of multiple personalities. Neither does dissociative identity disorder allow the various personalities to work as a team to fight bad guys or claim victory over one another just so the nice personality can marry the girl.
What About Bob? is a very special movie in that its main character has more than one psychological disorder, including OCD and several phobias. Actually, pretty much every character in the film has some form of mental illness, including avoidant and paranoid personality disorders. While Dr. Marvin's paranoid condition is aggravated to the point of attempted murder because of Bob's dependent personality disorder, the doctor's extreme dislike for Bob somehow leads to his cure.
In the real world, treatment of Bob's personality disorder would require medication and several years of psychotherapy, not a relaxing vacation that includes being tied to a ship mast in order to conquer his fears.
Bradley Cooper's character has recently been released from a mental health facility after seeking treatment for bipolar disorder. His violent outbursts cause his ex-wife to put distance between them and he is so focused on getting her back, he won't give Jennifer Lawrence's character (who has depression) a chance. They are eventually brought together - and a majority of their problems are solved - when they agree to enter a dance competition. Because nothing solves mood swings like the mambo.
In reality, since bipolar disorder can also be associated with anxiety and psychosis, it's important to get diagnosed and be treated with medication and psychotherapy, not learn to tango.
Even though A Beautiful Mind is based on the real-life story of John Nash, a math genius who won a Nobel Prize for Economics, its depiction of his struggles with paranoid schizophrenia was called out by some for its inaccuracy. While Russell Crowe's character experiences visual hallucinations in the film, it's extremely rare for a real life schizophrenic to find themselves hallucinating anything other than voices or other auditory events.
Psychiatrists gave Crowe a little slack due to Nash's high IQ, but claim the majority of schizophrenic patients cannot recognize their hallucinations aren't real and simply will themselves to stop them. Although Nash does take drugs in the film in addition to his apparent self-management, schizophrenia is treated mainly through life-long medication and can't be cured.