Decompensation is when someone with a mental illness, who was maintaining their mental illness well, starts to worsen. Signs that decompensation is occurring are a worsening of symptoms, inability to cope with stress and change, and difficulty with normal life situations like social situations and financial issues.
Patients experiencing decompensation have an inability to maintain normal psychological functions and defenses. Some causes of decompensation are if the current mental treatments are no longer working or a new cognitive issue arising. For example, in a person with schizophrenia decompensation could occur when delusions, hallucinations, and a deterioration of social interactions occur. This could be due to medication no longer being effective in the patient.