Exploring the links between cannabis use and mental health ;An analysis of primary care data in Colorado, California and Oregon states

Anne Campbell, dennis mc carty, Steffani Bailey

Research output: Contribution to journalArticlepeer-review


Cannabis is the most popular drug of choice in the US as recently reported in the CBHSQ report ( CBHSQ 2016 ). The national survey highlighted that 22.2 million Americans (8.3% of total population of 256 million) reported that they had used cannabis in the past thirty days. This is in comparison with illicit use of prescribed medication (3.8 million), stimulants (1.7 m) and heroin (0.3 million).
The primary aim of the study was to consider the associations between the reporting of cannabis use and the recording of mental health conditions within a sample of EHRs in three US states. In addition, a further aim of the study was to ascertain if the method of recording cannabis use changed the strength of the relationship between recorded cannabis use and recorded mental health disorders.
This was accomplished using EHR data from OCHIN, a non-profit community health information network providing a single Epic© electronic health record to a network of Community Health Centres (CHCs) spanning 18 states. The data was extracted from OCHIN clinics in OR, WA and CA from 2005-2016. The population included Adult (18 to 64 years of age) CHC patients with one or more visits to one or more of the participating CHCs. The current study interrogated the same database and considered individual case data relating to 88,111 patients from 2012-2016.

It is clear from the results that there is a stronger association between formally recorded cannabis use via the ICD 9/10/ diagnostic codes and mental health disorders than that which considers the less rigorously recorded social history variable (which records cannabis use haphazardly at any point within the EHR). A consideration of the relationship between schizophrenia and cannabis use in the literature is largely consistent with the results from the current study (OR, 3.66; CI= 3.45-3.87) showing a greater level of association between cannabis use as recorded in the problem encounter list with the EHR and schizophrenia.
The odds ratio for cannabis use as recorded in the problem list / encounter variable and the association with depression was (OR= 1.85 CI= 1.79-1.91). This indicates that those who are recorded as using cannabis are almost twice as likely to have recorded depression in the HER.
The consideration of recording on patient health care records needs attention as it is clear that a more focused recording of data in relation to cannabis use via diagnostic criteria facilitates a more focused analysis on the relationship between cannabis use and mental health disorders. It is important to record the diagnosis of cannabis use via ICD 9 and 10 codes which indicate more harmful use of the drug. It therefore follows that if we are screening for more harmful levels of cannabis use in primary health care services in conjunction with a consideration of co morbidity this should be accompanied by brief intervention specifically designed for co morbid disorders, which may ensure a more successful pathway of referral on to more specialised services. In addition, in the context of the increased use of cannabis by a greater number and in some cases at more harmful level across all age groups , a more informed understanding of the relationship between cannabis use and mental health disorders will also have a huge positive impact on public health policy .
Original languageEnglish
Publication statusIn preparation - 30 Jul 2018
Externally publishedYes


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