Another criticism is that the definitions used for criteria lack consistency; this is particularly relevant to the evaluation of delusions and thought disorder. More recently, it has been argued that psychotic symptoms are not a good basis for making a diagnosis of schizophrenia as "psychosis is the 'fever' of mental illness — a serious but nonspecific indicator".
Perhaps because of these factors, studies examining the diagnosis of schizophrenia have typically shown relatively low or inconsistent levels of diagnostic reliability. Most famously, David Rosenhan's 1972 study, published as On being sane in insane places, demonstrated that the diagnosis of schizophrenia was (at least at the time) often subjective and unreliable. More recent studies have found agreement between any two psychiatrists when diagnosing schizophrenia tends to reach about 65% at best. This, and the results of earlier studies of diagnostic reliability (which typically reported even lower levels of agreement) have led some critics to argue that the diagnosis of schizophrenia should be abandoned.
In 2004 in Japan, the Japanese term for schizophrenia was changed from Seishin-Bunretsu-Byo (mind-split-disease) to Tōgō-shitchō-shō (integration disorder). In 2006, campaigners in the UK, under the banner of Campaign for Abolition of the Schizophrenia Label, argued for a similar rejection of the diagnosis of schizophrenia and a different approach to the treatment and understanding of the symptoms currently associated with it.
Alternatively, other proponents have put forward using the presence of specific neurocognitive deficits to make a diagnosis. These take the form of a reduction or impairment in basic psychological functions such as memory, attention, executive function and problem solving. It is these sorts of difficulties, rather than the psychotic symptoms (which can in many cases be controlled by antipsychotic medication), which seem to be the cause of most disability in schizophrenia. However, this argument is relatively new and it is unlikely that the method of diagnosing schizophrenia will change radically in the near future.
The diagnosis of schizophrenia has been used for political rather than therapeutic purposes; in the Soviet Union an additional sub-classification of sluggishly progressing schizophrenia was created. Particularly in the RSFSR (Russian Soviet Federated Socialist Republic), this diagnosis was used for the purpose of silencing political dissidents or forcing them to recant their ideas by the use of forcible confinement and treatment. In 2000 there were similar concerns regarding detention and 'treatment' of practitioners of the Falun Gong movement by the Chinese government. This led the American Psychiatric Association's Committee on the Abuse of Psychiatry and Psychiatrists to pass a resolution to urge the World Psychiatric Association to investigate the situation in China.
Schizophrenia occurs equally in males and females although typically appears earlier in men with the peak ages of onset being 20–28 years for males and 26–32 years for females. Much rarer are instances of childhood-onset and late- (middle age) or very-late-onset (old age) schizophrenia. The lifetime prevalence of schizophrenia, that is, the proportion of individuals expected to experience the disease at any time in their lives,