"The dearth of literature on this topic means that coerced medication is not an evidenced-based practice," say researchers in a review published last month in the Journal of Advanced Nursing.

"Much more research is needed in examining all aspects of this contentious practice,” wrote the authors who include Len Bowers, professor of Psychiatric Nursing at City University in London.

The review was based on peer-reviewed studies from 1980 to 2008. In all 14 research papers from seven countries were reviewed.

A failure to comply with psychiatric medication is associated with quicker relapse and a more chaotic lifestyle, wrote the review's authors.

Patients who have been treated under compulsion are usually in their 30s, with a diagnosis of schizophrenia, bipolar or other psychotic disorders. They are often involuntarily admitted.

Assault or threat of assault is the main reason for forcibly medicating a patient, stated the review.

Reasons patients gave for refusing medication, usually antipsychotics, included side effect concerns, believing they were well enough and did not need medication, fearing the medication was poison, and fearing becoming addicted to the medication.

Some studies have examined patients’ retrospective views about whether they agreed with having been given medication against their will.

One 1996 study found 18 (60%) of 30 patients agreed that forced medication was right for them. And 13 (43%) stated they should be forced again if in a similar state. Sixteen (53%) said that they would be more likely to take medication voluntarily in the future. But 13 (43%) believed psychiatrists should not be allowed to force medication on patients. In a 2003 study of 10 patients, just three retrospectively agreed that their enforced medication was right.

The Mental Health Act, which came into effect in November last year, increased compulsion powers with the introduction of community treatment orders which obliges patients living outside hospital to take psychiatric medication. Some campaigners fear such orders risk driving patients away from mental health services. The government argued such orders would only effect a minority of “revolving door” patients.