Almost 10 million British adults are diagnosed with at least one mental health problem every single year, research suggests, making psychiatric treatment one of the biggest issues affecting society today.
The figure - which equates to one in four adults in the UK - is largely made up of those suffering anxiety and depression, as well as obsessive compulsive disorder and various phobias.
The Office for National Statistics (ONS) has also estimated that in 10 children aged between five and 16 have a clinically diagnosed mental health disorder, with the highest number - six per cent - affected by a conduct or behavioural problem.
Three per cent have been diagnosed with anxiety and one per cent with depression, according to the 2004 figures - while disorders such as autism, tics and eating problems make up less than one per cent.
Globally, the World Health Organisation estimates that around 450 million people are affected by mental health issues.
And the challenge for healthcare professionals comes from more than simply trying to treat the mental health problem itself.
Often, such disorders are linked somehow to physical disease or health conditions. Some 30 per cent of those suffering from a long-term physical health consition also have a diagnosable mental health condition.
People with a psychological disorder are almost twice as likely to die from coronary heart disease as the average person, and four times as likely to die from respiratory disease.
They are also at higher risk of being overweight or obese.
According to estimates from Rethink Mental Illness, around 33,000 - a third - of the 100,000 'avoidable deaths' amongst under-75s in the UK involve someone with a mental disorder.
Children and teenagers who suffer with mental health issues and do not receive proper support have been found to have worse prospects into adulthood.
Those with mild conduct problems during adolescence, for example, have double the chance of ending up with no qualifications by their early adulthood.
And those with severe conduct problems are up to four times as likely to have been arrested by the age of 30.
Meanwhile, Homeless Link estimates around 70 per cent of people accessing help for homeless services have a mental health problem.
And a study of 1,435 newly-sentenced prisoners carried out by the Ministry of Justice in 2013 found that 16 per cent showed signs of psychosis, while nearly half were judged to be at risk of having anxiety or depression.