Scientific literature reviews aim to summarize the state of knowledge and published empirical evidence. In contrast, medical guidelines are intervention tools that aim to improve physician behaviour and patient outcome. They can have positive effects, but they can also have negative effects. Their effects must be tested by research.

In a randomized controlled trial, 103 psychiatrists in private practice were either provided with the WHO depression guideline only (information group), or provided with the WHO depression guideline and trained for one day in this guideline (intervention group), or left uninformed (control group). They then treated a total of 497 patients according to individual clinical considerations and the needs of the patients. Observation of routine treatment lasted 12weeks. Physicians and patients documented the course of illness and treatment, including the patient–physician interaction.

Psychiatrists in the intervention group saw more psychosocial stressors in their patients, prescribed higher dosages of medication, had fewer drop-outs, and rated treatment outcome as better. The ratings of patient–physician interactions indicated more strain in their relationships.

The results show both positive and negative effects of guideline exposure, but only in the training group and not in the information group. Guidelines should be empirically tested before being called “evidence based”. Every guideline should also explain how it can or must be implemented in order to become effective.