Psychiatric symptoms of organic disorders

Table 1 shows some of the organic illnesses in which psychiatric symptoms occur as a direct result of the organic disease process. ICD10 classifies such episodes as ‘other mental disorders due to brain damage and dysfunction and physical disease’. By ‘other mental disorders’, it means disorders other than dementia, amnesic syndrome and delirium which are also due to brain damage and dysfunction or physical disease. It splits these other mental disorders into subgroups, depending on the nature of the psychiatric symptoms caused by the organic disorder. Examples of these subgroups include:

organic hallucinosis

organic delusional disorder

organic mood disorder

organic anxiety disorder.

Table 1 Organic causes of psychiatric symptoms

The possibility of an organic cause should always be kept in mind when assessing patients with psychiatric symptoms. There may be clues that the patient has an organic disorder, as summarised in Figure 2. As an example, think of the differential diagnosis of a patient with episodes of anxiety and breathlessness. These symptoms are often caused by panic disorder. However, it would be important to look for symptoms and signs of organic disorders known to cause anxiety. For instance, the patient might also show evidence of heat intolerance and brisk deep tendon reflexes, in which case hyperthyroidism should be considered. An unusual description of symptoms might also suggest a medical cause. For instance, if their anxiety was mild and seemed to be secondary to their breathlessness, a cardiac or respiratory cause should be considered. An unusual presentation should also lead you to suspect a medical cause. For instance, first onset of panic disorder would be very unusual in a 50-year-old man with no previous psychiatric history and no recent stresses or adverse life events. With such a presentation, organic causes should be investigated fully.

Fig. 2 Six factors which suggest an organic cause of psychiatric symptoms.

Recognition of medical disorders presenting with psychiatric symptoms is clearly important as the patient will not usually recover until the underlying medical condition has been treated. Symptomatic treatment with psychotropic drugs may be required before the medical disorder has been treated. Psychotropics may also be needed if the medical disorder is untreatable, or if psychiatric symptoms persist after successful treatment of the medical condition.