Psychosis usually develops gradually over a period of time. It can happen that psychosis starts suddenly but this is not common, it generally occurs in three phases.
Psychosis usually develops in late adolescence or early adulthood. This is generally a time of change for a young person so it can be difficult to recognise the difference between changes that are happening during normal development and changes that occur because of psychosis developing. However, there are common early warning signs that may happen before a first episode of psychosis. These changes can last for months but each persons experience will differ and not everyone will experience all of the "common signs".
The acute phase is when the symptoms of psychosis begin to emerge. It is during this stage that the symptoms of psychosis are most noticeable and when the individual experiencing psychosis or their families begin to look for help.
Some of the symptoms that are apparent in the acute phase may linger in the recovery phase but with appropriate treatment most people successfully recover and return to their normal, everyday lives.