General practitioners in the UK are being urged to do more to spot signs of depression and anxiety to help millions of people who are currently undiagnosed.

At any one time, one in six adults suffers a common mental health condition such as depression, generalised anxiety disorder or obsessive compulsive disorder.

Other common conditions include panic disorder, social anxiety and post-traumatic stress disorder, which is thought to be hugely under-diagnosed.

New guidance from the National Institute for Health and Clinical Excellence aims to improve detection of the conditions.

Experts said there was not enough evidence to suggest screening the whole patient population but GPs should ask simple questions if they suspect somebody is struggling.

Patients may also be asked if they are unable to stop or control worrying thoughts, possibly indicating an anxiety disorder.

GPs should also consider asking people who may have depression two questions: During the last month, have you often been bothered by feeling down, depressed or hopeless? During the last month, have you often been bothered by having little interest or pleasure in doing things?

If the patient says ‘yes’, then the doctor is likely to ask further detailed questions.

Figures suggest that people with long-term conditions such as diabetes are three times more likely to experience depression than the general population.

Estimates of the proportion of people who are likely to experience disorders during their lifetime are from four per cent to 10 per cent for major depression, 2.5 per cent to five per cent for chronic depression, 5.7 per cent for generalised anxiety disorder and 1.4 per cent for panic disorder.

The figure is 12.5 per cent for specific phobias, 12.1 per cent for social anxiety disorder, 1.6 per cent for OCD and 6.8 per cent for PTSD.

However, research suggests only about 30 per cent of people with depression are identified in GP surgeries, with another 30 per cent never coming forward for help.

Fewer than one in 10 people with anxiety are likely to be identified by GPs.

Professor Tony Kendrick, chairman of the Nice guideline development group, said GP services “do vary but are getting better” when it comes to mental health.

He added: “The costs of common mental health disorders are very high. They are estimated to cause one in five days lost from work in Britain.

“There are existing problems with identification of people with the disorders and with access to primary and secondary care.

“At present general practitioners have to consult several different disorder-specific guidelines when presented with patients with these problems, which makes it difficult to access the relevant information.

“This new guideline can be used by GPs as a handy guide to initial identification and referral, with quick reference points to the disorder-specific guidelines for details of treatment.”

Barbara Compitus, a GP from Southville in Bristol, told how it had taken one of her patients two years to pluck up the courage to seek help, and they had only done so after realising every day was “like a living nightmare”.

Another patient realised they needed to tackle their OCD when it got to the point where it was taking them two hours to leave the house.

They also would not go out without putting the iron in their bag to prevent a house fire.

Stephen Pilling, professor and director of the National Collaborating Centre for Mental Health, said: “This guideline will ensure that effective treatments are made available to people with depression and a range of anxiety disorders.

“This is important because, untreated, the outcomes of these conditions are serious.

“For example, depression is the commonest cause of suicide in this country. But if people receive appropriate treatment, as outlined in this guideline, they get better.”

Paul Farmer, chief executive officer of the mental health charity Mind, said many people suffered because their symptoms were not picked up or the treatment they needed was not available.

“Receiving a diagnosis and following this up with the right type of care can be key in determining whether someone progresses towards recovery or whether their mental health further deteriorates.”