This survey, conducted by the University of Michigan with support from the National Institute of Mental Health, included 9,282 households selected at random in 34 states. Nearly 300 trained interviewers traveled about 8 million miles over a year and a half. They knocked on doors at all hours of the day and night to ensure they would not systematically miss alcohol abusers who spend their days at bars, people with depression who can go weeks hardly able to pull themselves out of bed and people with social phobia who only rarely answer the door.

• Almost half of all Americans meet the criteria for a mental illness at some point in their lives. Most cases are mild and probably do not require treatment.

• 1 in 25 of all Americans met the criteria for having a mental illness within the past year.

• One-quarter of those had a serious disorder that significantly disrupted their ability to function day to day.

• About 6 percent of adults are so seriously affected by a mental illness that they cannot perform even routine activities for periods averaging three months.

• Less than half of those who need treatment receive it.

• 17 percent of the population was treated for mental illness over a 12-month period, up from 13 percent a decade ago, with the greatest increase coming from primary care physicians providing psychiatric services.

• People with a mental or substance abuse disorder were more likely to get treatment from a primary care physician/nurse or other general medical doctor (22.8 percent), or from a non-psychiatrist mental health specialist (16 percent), such as a psychologist, social worker or counselor. Only 12 percent of those who received treatment saw a psychiatrist.

• Approximately 9.7 percent of those with mental or substance abuse disorders sought help from a counselor or spiritual advisor outside of a mental health setting.

• 6.9 percent of those with mental or substance abuse disorders used a complementary-alternative source such as a chiropractor or self-help group.

• Those who do receive treatment typically do so after a decade or more of delays, during which time they are likely to develop additional problems.

• The median delay in getting treatment for all mental disorders is 10 years.

• The longest delays are 20 to 23 years for social phobia and separation anxiety disorders, possibly due to the relatively early onset and fears of therapy that involve social interactions.

• People with mood disorders do not receive treatment for six to eight years.

• The pattern appears to be that the earlier in life the disorder begins, the slower an individual is to seek therapy and the more persistent the illness. (Dr. Kessler)

• Half of those who will ever be diagnosed with a mental disorder show signs of the disease by age 14, and three-quarters by age 24.

• Nearly half of people with one mental disorder meet the criteria for two or more.

• Over a 12-month period, 60 percent of those with a mental disorder received no treatment.

• Approximately one-third of people in need rely solely on nonprofessional sources such as Internet support groups and spiritual advisors.