Some 55% of people who survive intensive care treatment go on to develop psychological disorders, British researchers have found.

A study of 157 patients at University College Hospital, in London, found high levels of depression, anxiety and post traumatic stress disorder.

Critical Care Journal reports certain drugs combined with stress in hospital seemed to cause longer term problems.

Doctors want to trial reducing stress and altering drugs in intensive care.

Dr Dorothy Wade, a psychologist from University College London, said: "The focus of intensive care is to save lives, to do whatever it takes."

However, she said, it could be a traumatic experience for some patients.

"Once they're starting to wake up and become conscious they can be in a terrified state, thinking they've gone mad or there's a conspiracy to steal their organs or to torture them."

Lasting impact

The study found that three months later, 55% of the 157 patients had some form of psychological problem - 27% had post-traumatic stress disorder, 46% had depression and 44% had anxiety.

The risk of developing the disorders increased depending on how long patients were sedated for and the drugs they were taking, such as those used for controlling blood pressure.

Patients with sleep deprivation, hallucinations and nightmares were also at risk.

Dr Wade said she was "really surprised" at how high the rates were.

She added: "As well as looking at modifying our drug treatments, we may need to invest more time in the psychological care of a patient and find ways to prevent psychological suffering in the intensive care unit which can affect the quality of their life in years to come."

Dr David Howell, who is the clinical director of critical care at the hospital, said: "It is fair to say there hasn't been enough focus on the psychological aspects of recovery in intensive care and afterwards."

He said the study had established the scale of the problem and the big question now was: "How can we make that better?"

Bob Winter, president of the Intensive Care Society, which represents doctors in the field, said: "This is clearly an important study confirming in some cases what we have known in intensive care for some time, that what we do for patients has a psychological impact that extends well beyond their intensive care stay.

"What is interesting about this study is the fact that some of the associations seem to be modifiable.

"The association of benzodiazepine use with subsequent psychological symptoms has important implications for sedative practice in intensive care. There are also implications for how we make our interventions tolerable in terms of how we can reduce the duration of sedation."