Psychology Issues and Debates

most common mental disabilities

Major depression is one of the most common mental disorders in the United States.

According to the World Health Organization (WHO; 2010), major depression also carries the heaviest burden of disability among mental and behavioral disorders. Specifically, major depression accounts for:

The 12-month prevalence data for major depressive episode presented here are from the National Survey on Drug Use and Health (NSDUH). Based mainly on the 4th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV), in the NSDUH study a major depressive episode is defined as:

A period of two weeks or longer during which there is either depressed mood or loss of interest or pleasure, and at least four other symptoms that reflect a change in functioning, such as problems with sleep, eating, energy, concentration, and self-image.

Unlike the definition in the DSM-IV, no exclusions were made for a major depressive episode caused by medical illness, bereavement, or substance use disorders.

In 2015, an estimated 16.1 million adults aged 18 or older in the United States had at least one major depressive episode in the past year. This number represented 6.7% of all U.S. adults.

Statistical Methods and Measurement Caveats

Diagnostic Assessment:

Modules related to major depressive episode derived from DSM-IV (APA, 1994) criteria for major depression were included in the NSDUH questionnaire. The adult questions were adapted from the depression module in the National Comorbidity Survey Replication (NCS-R). Revisions to the questions in the modules were made primarily to reduce their length and to modify the NCS-R questions, which are interviewer-administered, to the audio computer-assisted self-interviewing (ACASI) format used in NSDUH. In addition, some revisions, based on cognitive testing, were made to improve comprehension. Furthermore, even though titles similar to those used in the NCS-R were used for the NSDUH modules, the results of these items may not be directly comparable. This is mainly due to differing modes of administration in each survey (ACASI in NSDUH vs. computer-assisted personal interviewing [CAPI] in NCS-R), revisions to wording necessary to maintain the logical processes of the ACASI environment, and possible context effects resulting from deleting questions not explicitly pertinent to major depression.

Some questions in the adult depression module differ slightly from questions in the adolescent depression module; as such, major depressive data for adults aged 18 or older should not be compared to or combined with MDE data for youths aged 12 to 17.

Population:

The entirety of NSDUH respondents for the major depressive episode estimates is the civilian, non-institutionalized population aged 18 years old or older residing within the United States.

The survey covers residents of households (persons living in houses/townhouses, apartments, condominiums; civilians living in housing on military bases, etc.) and persons in non-institutional group quarters (e.g., shelters, rooming/boarding houses, college dormitories, migratory workers' camps, and halfway houses).

The survey does not cover persons who, for the entire year, had no fixed address (e.g., homeless and/or transient persons not in shelters); were on active military duty; or who resided in institutional group quarters (e.g., correctional facilities, nursing homes, mental institutions, long-term hospitals).

Some people in these excluded categories may have had a major depressive episode in the past year, but they are not accounted for in the NSDUH major depressive episode estimates.

Survey Non-response:

In 2015, 30.7% of the selected NSDUH sample did not complete the interview.

Reasons for non-response to interviewing include: refusal to participate (22.2%); respondent unavailable or no one at home/not answering the door (3.9%); and other reasons such as physical/mental incompetence or language barriers (4.6%).

People with major depressive episode may disproportionately fall into these non-response categories. While NSDUH weighting includes non-response adjustments to reduce bias, these adjustments may not fully account for differential non-response by mental illness status.

Please see the Results from the 2015 SAMHSA NSDUH Mental Health Findings for further information on how these data were collected and calculated.