A mental disorder that causes "crippling shyness" in social or work situations often begins in early adolescence and isn't being treated, suggests a new study from Statistics Canada.

Based on information from the 2002 Canadian Community Health Survey: Mental Health and Well-being, the study shows symptoms of social anxiety disorder begin at an average age of 13.

Symptoms, which include feeling paralyzed in social or work situations, can last for an average of 20 years, according to the study. People with the disorder have an intense fear of being scrutinized or embarrassed, and try to avoid social encounters.

The early onset of social anxiety disorder is in contrast with two other common disorders, panic disorder and depression, in which symptoms usually begin in the mid-to-late 20s.

About eight per cent of Canada's population – slightly more than 2 million people – have reported a "lifetime history" of social anxiety disorder.

In 2002 alone, 750,000 people (three per cent of the population), reported symptoms of the disorder in the past year.

People with symptoms of the disorder, who are most likely people aged 15-24, have a higher risk of having depressive disorder, panic disorder and dependency on drugs and alcohol, suggests the study.

The disorder is also linked to lower educational attainment, decreased likelihood of marriage and employment, and increased dissatisfaction with life.

Symptoms are largely going unreported, it appears, as only 37 per cent reported seeking help or treatment.

"Sufferers may just be too inhibited by their social fears to seek help," says Statistics Canada. "They may be reluctant or embarrassed to discuss their symptoms, even with a health professional."

The study suggests many people with social anxiety disorder may not be aware they have a recognized mental disorder, thinking they are simply shy.