The number of adults being treated for obsessive compulsive disorders (OCD) continues to rise, prompting experts to call for more support for sufferers and their families.

Latest figures from the Institute of Mental Health (IMH) show that 850 adults were treated for the condition as of November last year, up from 640 in 2010.

The first and only Singapore Mental Health Study released in 2011 found that Singapore was the OCD capital of the world, with higher rates of the illness compared with the United States or Europe.

This number is likely to be the tip of the iceberg as OCD often goes undiagnosed and nine out of 10 people who have OCD do not get any sort of treatment.

Health experts say the silent and lonely scourge not only exacts its toll on sufferers, but also drags family members who live with them into their private hell.

Last month, it was revealed in court that a Singaporean employer alleged to have starved her maid had OCD and treated cleanliness "like a religion". Her husband said one of their sons ran away from home because of her tendencies.

The family also showered in a public toilet by the swimming pool and camped out in the living room to save time from having to clean their bathroom or rooms as thoroughly as she would have wanted it.

OCD is an anxiety affliction characterised by obsessions, compulsive rituals, and intrusive thoughts and impulses. While IMH attributed the increase in adult OCD cases to a rise in awareness of the condition, psychiatrists say the impact of the disorder on family members is often overlooked.

"Patients with severe OCD can be controlling and demanding, and insist that family members participate in their OCD behaviours," said Dr Adrian Wang, consultant psychiatrist at Gleneagles Medical Centre.

"I have seen people who have had to spend hours checking the locks and doors of their homes together with their OCD spouses, and parents banned from entering their OCD children's bedrooms because the child fears that anything the parent touches may result in contamination."

Dr Thomas Lee, medical director and consultant psychiatrist at The Resilienz Clinic, said: "The family can become mentally and physically exhausted... It is not uncommon for the loved ones of OCD patients to suffer psychological issues such as depression or suicidal thoughts."

Dr Lee recalled treating a patient who feared contaminated food and utensils. He ate food prepared only by his mother as it had to be cooked in a certain manner, using only specific utensils.

"His mother had to succumb to his demands because he could turn violent towards the family. As a result, she suffered depression and became physically ill," said Dr Lee.

Dr Jayaraman Hariram, consultant at IMH's department of community psychiatry, said: "Family members may become deeply involved in the person's rituals and may have to assume responsibility and care for many daily activities that the person with OCD is unable to undertake. This can cause distress and disruption to all members of the family."

OCD is among the top three most common mental disorders here, with about 3 per cent of the population - or one in 33 people here - suffering from it, according to the Singapore Mental Health study by IMH. This is higher than the rate in the United States (2.3 per cent) or Europe (1.1 per cent).

The common obsessions seen are being overly concerned with dirt or contamination, having unpleasant sexual thoughts, fear of causing harm to self or others, and fear of losing things. Sufferers perform repetitive actions such as excessive washing and cleaning, checking, counting or arranging things to ease their anxiety. The disorder tends to run in families and can be brought on by certain illnesses or stressful life events. It can be treated with drugs and behavioural therapy.

The IMH set up an OCD clinic last year to see severe and chronic patients. For patients who are unable to even leave their homes because of the severity of their condition, its staff make home visits. "The strain on caregivers of patients with OCD very often does not come into the limelight," said Dr Hariram. "It is important to note that the family is not helping in the long run by accommodating the patient with OCD."

That is why psychologists from IMH try to involve the family members in the therapy process. The hospital is also working with other voluntary agencies to set up support groups tailored for patients with OCD and their families.

Dr Lee said: "Engaging the family offers a better chance for recovery. They need to muster the courage to seek professional help for themselves and for the patient. Otherwise, it is unlikely that the situation at home will improve because OCD can worsen with time."