The first step in a complete assessment is to review the history, physical examination, and laboratory tests. The thorough clinician not only looks for a temporal correlation (e.g., the onset of a psychosis shortly after starting or increasing the dose of a medication), but also keeps in mind well-documented associations between certain mental symptoms (e.g., depression) and certain general medical conditions (e.g., Cushing’s syndrome). If it appears, at this point, that the mental symptoms could indeed be occurring secondary to a medical condition, the next step involves determining whether or not these symptoms could be better accounted for by a primary psychiatric disorder.

In cases where the mental symptoms do not present an emergency, one looks to whether the underlying medical condition is treatable. If the underlying condition is not treatable, one generally proceeds directly to symptomatic treatment. In cases where the underlying condition is treatable, one must make a judgment as to whether, with treatment of the medical condition, the mental symptoms will resolve at a clinically acceptable rate. For example, in the case of a patient with anxiety due to hyperthyroidism who has just begun treatment with an antithyroid drug, the decision as to whether to offer a benzodiazepine as symptomatic treatment for the anxiety depends not only on the severity and tolerability of the anxiety, but also on the expected time required for the antithyroid drug to resolve the hyperthyroidism; here, clearly, considerable clinical judgment is required.

23.3.1 Clinical Patterns

A psychotic disorder due to a general medical condition is characterized clinically by hallucinations or delusions occurring in a clear sensorium, without any associated decrement in intellectual abilities. Furthermore, one must be able to demonstrate, by history, physical examination, or laboratory findings, that the psychosis is occurring on the basis of a general medical disorder.

Box 23.1 lists the various secondary causes of psychosis, dividing them into those occurring secondary to precipitants (e.g., medications), those occurring secondary to diseases with distinctive features (e.g., the chorea of Huntington’s disease), and finally a group occurring secondary to miscellaneous causes (e.g., cerebral tumors).

Psychosis occurring secondary to precipitants is perhaps the most common form of secondary psychosis. Among the various possible precipitants, substances (drugs of abuse) are perhaps the most common. These are considered in the chapters on stimulants, hallucinogens, phencyclidine, cannabis, and alcohol. After drugs of abuse, various medications are the next most common precipitants, and the most problematic are the neuroleptics themselves. It appears that, in a very small minority of patients treated chronically with neuroleptics, a “supersensitivity psychosis” (or, as it has also been called, on analogy with tardive dyskinesia, “tardive psychosis”) may occur. Making such a diagnosis in the case of patients with schizophrenia may be difficult, as one may well say that any increase in psychotic symptoms, rather than evidence for a supersensitivity psychosis, may merely represent an exacerbation of the schizophrenia. In the case of patients treated with antipsychotics for other conditions (e.g., Tourette’s syndrome), however, the appearance of a psychosis is far more suggestive, as it could not be accounted for on the basis of the disease for which the neuroleptic was prescribed. Of the dopaminergic drugs capable of causing a psychosis, levodopa is the most common, and although direct-acting dopamine agonists such as bromocriptine and lergotrile and pramipexole may also be at fault, they are much less likely causes than is levodopa itself. The other medications noted in Box 23.1 only very rarely cause a psychosis.

Of the encephalitides that may have a psychosis as a sequela, the most classic is encephalitis lethargica (von Economo’s disease), a disease that, though no longer occurring in epidemic form, may still be seen sporadically. Other encephalitides, such as herpes simplex encephalitis, may also (albeit rarely) have a psychosis as one of their sequelae.

Of the psychoses secondary to diseases with distinctive features, the psychoses of epilepsy are by far the most important, and these may be ictal, postictal, or interictal. Ictal psychoses represent complex partial seizures and are immediately suggested by their exquisitely paroxysmal onset.

Postictal psychoses are typically preceded by a “flurry” of grand mal or complex partial seizures and, importantly, are separated from the last of this “flurry” of seizures by a “lucid” interval lasting from hours to days. Interictal psychoses appear in one of two forms, namely, the psychosis of forced normalization and the chronic interictal psychosis. The psychosis of forced normalization appears when anticonvulsants have not only stopped seizures but have essentially “normalized” the EEG: a disappearance of the psychosis with the resumption of seizure activity secures the diagnosis. The chronic interictal psychosis, often characterized by delusions of persecution and reference and auditory hallucinations, appears subacutely, over weeks or months, in patients with longstanding, uncontrolled grand mal or complex partial seizures.

Encephalitic psychoses are suggested by such typical “encephalitic” features as headache, lethargy, and fever. Prompt diagnosis is critical, especially in the case of herpes simplex encephalitis, given its treatability. The other specific features listed in Box 23.1 are fairly straightforward.

Of the miscellaneous causes capable of causing psychosis, cerebral tumors are perhaps the most important, with psychosis being noted with tumors of the frontal lobe, corpus callosum, and temporal lobe. Suggestive clinical evidence for such a cause includes prominent headache, seizures, or certain focal signs, such as aphasia. Cerebral infarction is likewise an important cause, and is suggested not only by accompanying focal signs, but also by its acute onset: infarction of the frontal lobe, temporoparietal area, and thalamus have all been implicated. Neurosyphilis should never be forgotten as a differential possibility in cases of psychosis of obscure origin. Vitamin B₁₂ deficiency should be borne in mind, especially as this may present with psychosis without any evidence of spinal cord or hematologic involvement. The remaining disorders listed in Box 23.1 are extremely rare causes of psychosis.

23.3.2 Assessment

In most cases, a thorough history and physical examination will disclose evidence of the underlying cause of the psychosis. When the patient’s symptomatology is atypical for one of the primary causes of psychosis (e.g., schizophrenia), yet the history and physical examination fail to disclose clear evidence for another cause, a “laboratory screen” as listed in Box 23.2 may be appropriate. Clearly, one does not order all these tests at once, but begins with those most likely to be informative, given the overall clinical picture.

23.3.3 Treatments

Treatment, if possible, is directed at the underlying cause. When such treatment is unavailable or ineffective, or where control of the psychosis is urgently required, neuroleptics are indicated. Although conventional neuroleptics, such as haloperidol, have long been used successfully, a second-generation antipsychotic (SGA), such as olanzapine or risperidone, may be better tolerated. In general, it is best to start with a low dose (e.g., 2.5 mg of haloperidol, 5 mg olanzapine, or 1 mg of risperidone) with incremental increases, if necessary, introduced slowly.

23.4.1 Clinical Patterns

A mood disorder with depressive features is characterized by a prominent and persistent depressed mood or loss of interest, and by the presence of evidence – from the history, physical examination, and/or laboratory tests – of a general medical condition capable of causing such a disturbance. Although other depressive symptoms (e.g., lack of energy, sleep disturbance, appetite change, psychomotor change) may be present, they are not necessary for the diagnosis. The various secondary causes of depression are listed in Box 23.3.

In using Box 23.3, the first question to ask is whether the depression could be secondary to precipitants. Of the various possible precipitants, substances of abuse (e.g., as seen in alcoholism or during stimulant withdrawal) are very common causes, and these are covered in their respective chapters. Medications are particularly important; however, it must be borne in mind that most patients are able to take the medications listed in Box 23.3 without untoward effect: consequently, before ascribing a depression to any medication it is critical to demonstrate that the depression did not begin before the medication was begun, and ideally, to demonstrate that the depression resolved after the medication was discontinued.

Anticholinergic withdrawal may occur within days after abrupt discontinuation of highly anticholinergic medications, such as benztropine or certain tricyclic antidepressants, and is characterized by depressed mood, malaise, insomnia, and gastrointestinal symptoms such as nausea, vomiting, abdominal cramping, and diarrhea. Poststroke depression is not uncommon, and may be more likely when the anterior portion of the left frontal lobe is involved; although spontaneous remission within a year is the rule, depressive symptoms, in the meantime, may be quite severe. Both head trauma and whiplash injuries may be followed by depressive symptoms in nearly half of all cases. Depression may occur secondary to diseases with distinctive features, and keeping such features in mind when evaluating depressed patients will lead to a gratifying number of diagnostic “pickups.” These features are noted in Box 23.3 and are for the most part self-explanatory; depression associated with epilepsy, however, merits some further discussion.