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Five-minute Practitioner: May 2009

Only got five minutes? Then just read these key points on: schizophrenia, depression and lithium toxicity

Only got five minutes? Then just read these key points on: schizophrenia, depression and lithium toxicity

Schizophrenia

Around 1 in 100 people will suffer from schizophrenia during their lifetime. Although the prognosis is highly variable, the condition tends to run a chronic course and is associated with considerable morbidity and mortality. It typically presents in late adolescence or early adulthood.

High-risk groups include: those who have a first-degree relative with schizophrenia, certain ethnic groups, adolescents, young adults and drug users.

Diagnosis should be made by a psychiatrist. It centres on clarification of psychopathology and exclusion of an organic cause. The GP plays a central role in providing a basic assessment, evaluating risk and identifying the most appropriate mental health resource.

Following their first episode of psychosis 15-20% of people will have no further episodes, 5-10% will have a largely treatment-resistant psychosis and the rest will have significant recovery but further episodes. To minimise the chance of relapse antipsychotics are continued for a minimum of 1-2 years and discontinued gradually. A second episode will generally necessitate prolonged, possibly lifelong, treatment.

A major cause of early mortality in schizophrenia is suicide, 10% of patients kill themselves. Suicide is most likely in the first few years following diagnosis, and it is important to be vigilant for depressive symptoms.

Physical health monitoring by GPs should be undertaken at least annually because patients with schizophrenia frequently have manifold risk factors for physical ill health, including smoking, excessive alcohol use and drug misuse, poor nutrition and hygiene, obesity, a sedentary lifestyle and poverty. The death rate from CVD in this population is roughly doubled.

Depression

Only a small minority of patients with depression receive effective treatment. Between 30 and 50% are not recognised as being depressed, usually as a result of somatic presentations.

The principal strategies for improving outcomes in depressed patients are: screening for depression in high-risk patients; increased awareness of somatic presentations of depression; use of a validated measure of depression severity to improve targeting of treatment and use of a care management programme to improve adherence to treatment.

The threshold of diagnosis of DSM-IV major depression marks a clinically important boundary above which antidepressants become more effective than placebo.

PHQ-9 is based on the DSM-IV criteria and is therefore a useful guide to severity. A validation study found that more than two-thirds of the patients with major depression had a score of ?15 and it is now recognised that a cut-off score of ?10 is too low and may encourage, rather than discourage, excessive prescribing.

Diagnosis of depression is complex and incorporates assessment of cognition, functional impairment, previous history, duration and illness trajectory as well as the number and severity of symptoms. It is a mistake to impose rigid treatment guidelines based solely on the PHQ-9 score. If the score is ?15, it is likely that the clinical suspicion of major depression is correct, but a score of 10-14 is borderline, and we need to think carefully before initiating antidepressant treatment.

Patients should be referred to psychiatric services if: there is a high suicide risk, psychotic major depression or major depression in bipolar affective disorder, or where two or more attempts to treat a patient with medication have failed.

Lithium toxicity

Careful monitoring of lithium levels is essential, in particular to prevent toxicity as lithium has a low therapeutic index. Older patients are especially vulnerable.

Lithium toxicity is often non-specific in presentation, and symptoms may be clouded by comorbidity in elderly patients. It may result from excessive lithium intake, either intentional or accidental, or reduced lithium excretion. The latter encompasses a range of conditions including dehydration, low sodium levels, renal disease or drug interactions.

Lithium toxicity is graded into mild, moderate and severe by clinical features, rather than serum lithium.

Regular use of lithium results in its accumulation within body tissues. Acute-on-chronic and chronic lithium toxicity is associated with an extent of baseline tissue saturation.

The National Poisons Information Service should be consulted in a case of poisoning. Haemodialysis is the cornerstone of treatment for severe lithium toxicity and should be considered in all patients with marked neurological features. Other supportive measures include ensuring hydration, correcting electrolyte imbalance and controlling convulsions with iv diazepam.

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