The typical cases of schizophrenia are easy to diagnose. The difficult to diagnose are those belonging to an ill-defined group that includes the so-called latent cases, borderline, character disorder, quasi-psychotic psychopaths, severe personality difficulties, and so on. The diagnosis made in these cases reflect more on the classificatory criteria of the psychiatrist than the symptomatology per se. Even in a typical case, the diagnosis may be difficult if the patient has been interviewed only once or twice on a consultation basis.
The first rule to be adopted in diagnosing schizophrenia is that an individual symptom or even a few symptoms should not be considered as absolute proof of the condition. The constellation of symptoms should be evaluated as the general picture they generate. Even symptoms that seem typical, like auditory hallucinations, delusions, or language disorders, should not be considered to be absolute proof of psychosis because they may occur in other organic or functional conditions. Very often, seriously disturbed, but not psychotic adolescents are often mistaken as schizophrenics.
Differential Diagnosis from Psychoneuroses
Differential diagnosis from psychoneuroses is easy in typical cases but is made difficult by the fact that neurotic symptoms may have preceded schizophrenia or may actually be present. When the personality as a whole undergoes a rapid decline or maladjustment, one must think of the possibility of a schizophrenic outcome, even though the previous symptomatology was neurotic. For instance, a sudden scholastic decline, dropping out, or any drastic transformation of character should be viewed with suspicion.
When hysteria was much more common than it is now, schizophrenia used to be confused with it. It is possible that the patients who were diagnosed in the past as hysterics were suffering from schizophrenia. Hysterical attacks occur more frequently in people with an extrovert personality and are characterized by conversion syndromes. The symptomatology is easily influenced by certain persons in the immediate environment and responds easily to hypnosis.
Differential Diagnosis from Manic-Depressive Psychosis
The diagnosis is easy in typical cases. Severe thought disorders, like illogical remarks, incongruous statements, bizarre delusions or ideas of reference, are rare in manic-depressive patients. When delusions occur, they are consequent to the mood with which they are congruous.
For instance, a patient suffering from psychotic depression may feel guilty for having committed alleged crimes, but this thought is part of a self-incriminating attitude. An elated manic patient may believe he is a millionaire. Manic excitement may be confused with that occurring in many schizophrenics. Manic excitement is sustained as long as the manic phase lasts, whereas, in schizophrenia, the condition is more acute and inconsistent. A catatonic excitement, in particular, may be confused with a manic state. However, in the manic state, the mood is more congruous and the actions, although grandiose, are less inappropriate. The anger of a manic patient, when he feels hindered or misunderstood, may be confused with the paranoid attitude of the schizophrenic. However, it generally lacks the suspiciousness, the innuendos, or the carefully conceived persecutory framework of the paranoid patient.
Differential Diagnosis from Psychopathic Personality
The differential diagnosis is easy with the presence of typical schizophrenic symptoms, such as delusions and hallucinations. It is difficult when it is based only on the behavior of the patient. In fact, antisocial behavior may be the result of both schizophrenia and psychopathic condition. In a psychopathic personality, the antisocial action has an easily recognizable aim: stealing, sexual gratification, revenge, and so on. Even when it could be demonstrated that the action had an unconscious symbolic meaning (for instance, stealing was a symbolic way to recapture the love of a mother that a sibling had stolen from the patient). The fact that the patient was also motivated at a conscious level and obtained or sought gratification at a conscious level is indicative of the likelihood of a psychopathic personality. On the other hand, if the antisocial behavior appears bizarre, absurd, and apparently unmotivated, the likelihood is that we are dealing with a schizophrenic psychosis, at times of a monosymptomatic type.
Differential Diagnosis from Organic Conditions
Many organic conditions have to be differentiated from schizophrenia, and all of them have to be taken into consideration by the examiner. We shall start with two that in recent years have been most frequently encountered in clinical practice: minimal brain damage and drug-induced syndromes.
Youngsters suffering from conditions variously called minimal brain damage, minimal cerebral dysfunction, and hyperkinesia may be difficult to differentiate from child schizophrenia or adult schizophrenia. Approximately half the patients who presented these conditions during childhood are sufficiently recovered by the end of their adolescence to escape psychiatric attention. A considerable number of them, however, continue even later in life to manifest constant or periodic excessive motor activity, at times slightly inappropriate behavior caused by restlessness, by the need to move, or by a lack of attention, and delay in the normal development of intellectual and emotional maturity.
The differential diagnosis of schizophrenia and psychoses due to drug abuse has recently become necessary. The use of lysergic acid diethylamide (LSD) may bring about clinical pictures similar to schizophrenia, during the immediate reaction to drug intake as well as in conditions caused by a prolonged adverse effect of the drug. In the presence of a history of LSD intake, the diagnosis is easy. Visual hallucinations with red, yellow, and blue colors occur much more frequently than in schizophrenia.
Differential Diagnosis from Miscellaneous or Unclassifiable Conditions
Occasionally, cases of Ganser syndrome are confused with cases of schizophrenia. The Ganser syndrome occurs generally, but not exclusively in prisoners who want to escape indictment. The patients often seem to have sustained memory losses. They appear bewildered, confused, and give answers reminiscent of the metonymic distortions of schizophrenics.
A condition, which in some cases is confused with schizophrenia is the Gilles de la Tourette’s disease. The patient presents jerking movements of the face and other parts of the body that resemble schizophrenic grimaces and mannerisms. Some patients also present coprolalia (impulsive use of profane words) or make unnatural harsh sounds.
Another condition that is to be differentiated from schizophrenia is the autoscopic syndrome or Lukianowicz phenomenon (Lukianowicz, 1958). The syndrome consists of the delusional experience of a double. The double is not a person from the patient’s environment but the patient himself. The patient sees a person who looks exactly like himself, talks, dresses, and acts as he does.
The Bottom Line
In diagnosing schizophrenia, many psychiatrists avail themselves of the help of clinical psychologists, especially projective tests such as the Rorschach, which may provide valuable information that is not available or deducible from the manifest symptomatology. Thus, the value of these psychological tests is particularly high at the beginning of treatment.