Validity of Timeline Follow-Back (TLFB) for self-reported use of cannabis and other illicit substances – systematic review of the literature

Introduction:
The Timeline Follow-Back (TLFB) instrument is used for assessing self-reported substance use. To our knowledge, no systematic review of the TLFB's validity for illicit drugs exists.

Research question:
How well does TLFB correlate with measures of consumption of cannabis and other illicit substances in comparison to biological measures such as blood or urine?

Methods:
PubMed, PsycINFO, CENTRAL, CINAHL, and EMBASE will be searched. Further articles will be obtained from reference lists and key researchers. Articles where illicit drug consumption has been measured both by TLFB and some biological measure will be included in the review.

Discussion:
The potential presence of publication bias will be assessed. The influence of factors such as psychiatric comorbidity and type of substance use on the validity of TLFB will also be assessed. It is expected that this systematic review will provide valuable insights into the validity of TLFB for cannabis and other illicit substances.