A mental health assessment must be based upon careful review of information from multiple sources and must measure a range of mental health concerns.

An assessment will be most effective when the information included is comprehensive and accurate. Using scientifically sound assessment tools helps assure that high quality information will be obtained. Researchers have developed many instruments that can provide consistent and meaningful results for these purposes.

To establish the scientific credibility of a psychological assessment tool, researchers must first demonstrate that it is reliable. In other words, it will yield consistently similar results if administered by different people, or if administered to the same person at different times. For example, if a person’s assessment results indicate depression when the assessment is done by Dr. Smith, then results should be the same when the assessment is done by Dr. Jones. Similarly, if a person is assessed with an instrument today that indicates s/he is depressed within the past month, then the results should be the same if that person is assessed again tomorrow.

Reliable assessment tools have standardized instructions that guide every person administering the instrument to use them in exactly the same way. This assures that every person taking the test will hear the same explanations.

In addition to establishing reliability, an instrument must have demonstrated that it is valid, or, that it measures what it claims to measure. For example, on a valid self-report test of depression, people who report a high level of depression on the test should also be rated as depressed by trained psychiatric clinical interviewers.