People become treatment resistant through repeated relapses over time, but a significant percentage are treatment resistant right from the start. The definition of treatment refractory or treatment resistant is technical but generally means the individual is having trouble with psychotic symptoms in spite of medication. A first episode, treated in the first six months, is ideal and generally has the best prognosis. It often takes much longer then 6 months to get someone treated partly because the public is so unfamiliar with what a psychosis is. With a gradual or insidious onset as it is called people tend to lose the human relationships that would help them get treatment.
Many people then develop a long history of going off their medication, and relapsing repeatedly.
For some it takes several relapses to realize the effectiveness of medication in preventing them. The following chart illustrates the impact of relapses on outcomes which isn't desirable. The main cause of relapse is noncompliance with medication. Many studies have shown this and the following chart from Lundbeck is a composite of many studies. EPS such as parkinsonism, akathisia and dystonia are movement disorders that occur through D2 dopamine blockade in the nigrostriatal regions of the brain and appear to lead to another more permanent movement disorder known as tardive dyskinesia which is irreversible.