The Impact of Cannabis Use on Medication Nonadherence in Psychiatry


Cannabis use disorder and nonadherence: How can we best educate patients?



Medication nonadherence has been one of the major barriers in patient care for psychiatrists managing patients with chronic mental health disorders.1 This has resulted in multiple negative outcomes including a protracted course of illness, worsening disease symptoms severity, risk of relapse suicide risk, illness exacerbation, mortality, and frequent hospitalizations.2 In addiction, medication nonadherence-related hospital readmissions increased the health care cost burden of the early 21st century to more than $100 billion per year, continuing to rise annually.3 However, one of the modifiable risk factors for medication nonadherence with possible interventions gaining traction is substance use disorder (SUD), particularly cannabis use disorder (CUD).4

Cannabis is one of the most frequently used drugs worldwide, and CUD has been rising substantially globally, especially in the Americas and Asia.5 CUD has become a growing problem in the United States since the passing of legislation permitting the medical use of cannabis in more than 33 states and recreational use in 11 additional states as of 2020.6 The overall percentage of patients who are nonadherent to their psychotropic medication was estimated to be 49% (56% with schizophrenia, 50% with major depressive disorders, and 44% with bipolar disorders).7,8 A recent study found that patients with first-episode psychosis who use cannabis were more prone to medication nonadherence and illness relapses compared to those who stopped using substances.9 A systematic review of 3678 patients with psychiatric illnesses also found cannabis users to have 2.5 times higher medication nonadherence to antipsychotic medications compared to non-cannabis users.4

Nonadherence is very challenging to tackle in the clinical setting, given its high prevalence. Nonadherence is usually identified after multiple relapses, misinterpretation data of medication efficacy, and several changes to prescription medications.10 However, there is evidence that cannabis use can be an early warning sign for future nonadherence and may be a good source for early intervention before a patient relapses.4

Typically, a urine drug screen (UDS) is done for screening patients who might have been using cannabis for several weeks in cases of chronic cannabis use. Delta-9-tetrahydrocannabinol (THC) and other cannabinoids metabolites can be detected in the urine of chronic heavy users of cannabis for up to 6 weeks. However, other active cannabinoids such as cannabidiol have less sensitivity to testing. What is crucial for clinicians to know is that a therapeutic alliance between the physician and the patient is key to managing patients with cannabis use and medication nonadherence.

Despite the availability of UDS tests, physicians should feel comfortable asking their patients about history of drug use utilizing techniques such as motivational interviewing. The interaction of cannabis and psychotropic medications should be described in clear terms to patients. Evidence has shown that the efficacy of antipsychotics in patients with psychosis and comorbid cannabis use is limited in the treatment of psychosis.11 There should be intentional education for patients about the negative effects of cannabis use. Clinicians must understand that CUD, like other SUDs, is a chronic relapsing disorder and some patients may have a difficult time attaining or maintaining sobriety. Sometimes it is helpful to offer patients shorter appointments to monitor periods of sobriety or complete abstinence during their treatment course. This also goes a long way to make patients feel like part of their treatment decisions.

Here we present 2 cases of patients with a history of chronic cannabis use and medication nonadherence to highlight the need for clinicians to spend more time educating their patients about substance use and offer other interventions to increase chances of abstinence.

Case Vignette 1

“Ms Monroe” is a young female patient with a history of anxiety disorder and major depressive disorder. Ms Monroe was diagnosed and prescribed with antidepressants and anxiolytic in the outpatient setting but reported multiple relapses due to poor compliance with her medications and heavy daily use of cannabis. She feels that smoking cannabis gives her relief from symptoms of anxiety and depression. Her increased use of cannabis over the years resulted in further deterioration of her mental health, as she was reported to be very paranoid and acting bizarre at presentation.

In the ER, she initially had hallucinations, then suddenly became completely mute and did not participate in any assessment. Ms Monroe was admitted to the inpatient, placed on appropriate precautions for the initial portion of hospitalization, and introduced to a therapeutic milieu. All labs and imaging studies were found to be within normal limit. She was diagnosed with catatonia. Ms Monroe responded to Ativan challenge and Ativan along with the addition of an antidepressants and antipsychotics. She responded well to the treatment, her catatonia completely resolved, her psychotic symptoms lessened, and her oral intake improved. While on the unit, she actively engaged in all aspects of treatment including individual and group/milieu therapy. Ms Monroe was educated about the negative physical and emotional effects of cannabis use. The team recommended she stop due to possible exacerbation of psychotic symptoms and concern for effects on efficacy of her medications. Motivational interviewing was employed and found to be very helpful. A significant improvement in patient insight regarding medication adherence and adverse effects of cannabis use was appreciated at the time of discharge.

Case Vignette 2

“Mr Walker” is a middle-aged male patient diagnosed with schizophrenia. Mr Walker was treated with antipsychotics for several years. He has a history of multiple relapses and hospitalization in the context of poor medication adherence and chronic cannabis use. Each time this patient is discharged with antipsychotic medications, he defaults on his care and goes back on the street to acquire street-available marijuana. His chronic cannabis use has often resulted in a relapse and therefore made him a frequent user of the mental health facility closest to him.

During his most recent admission, Mr Walker was asked if he would continue to use cannabis. He stated that he would not be able to say definitively until discharge from the hospital. Mr Walker was initially adamant about his care in the hospital but later started to participate in the treatment plan on the inpatient service. He was offered individual and group therapy sessions along with restarting his psychiatric medications. He was able to meet with the drug and alcohol use counsellor, who, over the duration of his stay in the hospital, was able to speak to him about quitting cannabis use, given his history of relapse and multiple hospitalizations. Different modalities were employed, including counseling, and scheduling short outpatient clinic appointments. At discharge, Mr Walker was sober and willing to engage with his psychiatric treatment while staying sober. He had a better insight into his psychiatric condition and understood the need to stop taking cannabis and be adherent to medication to prevent subsequent hospital admissions.


These 2 cases bring to light poor insight into a major issue among these patients. Often, patients do not think cannabis has anything to do with their mental illness. If anything, they think it helps their current mental health status improve. If clinicians spend more time educating their patients about substance use, its effects, and interactions with their medications, negative outcomes might be prevented. Both patients in these cases responded to antipsychotic and therapeutic milieu, but the problem is that patients often relapse once they get back on cannabis.

Different approaches have been implemented to improve psychotropic medication adherence among patients with chronic cannabis use. These include motivational interviewing (MI), cognitive behavioral therapy (CBT), use of smartphone apps, and augmentation with telepsychiatry. Implementation of evidence-based MI Style Adherence Therapy was found to be clinically significant in improving adherence to psychotropic medication (82% to 85%) in a Veterans Affairs Mental Health Clinic.12 MI intervention has shown improvement in psychotropic medication adherence from 43.9% to 70.7% in adolescents taking antidepressants and mood stabilizers.13

The usage of CBT strategies has shown to improve medication adherence and treatment outcomes in patients with bipolar disorder by increasing knowledge about medication and changing attitude toward treatment.14 Moreover, CBT use in another bipolar population study was shown to increase medication adherence and reduce relapse rates.15 Another study explored a combination of medication monitoring and CBT in increasing medication compliance in patients with bipolar disorder and comorbid SUD over 12 weeks compared to medication monitoring alone.16 The study found that adding CBT showed improved medication adherence and mood symptoms.16

Another possible intervention could be smartphone appsin using different modalities to enhance medication adherence. For instance, a study explored the use of smartphone app intervention in managing patients with type 2 diabetes medication nonadherence.17 The study showed that the smartphone app was user-friendly and had improved awareness of medication adherence. However, the app usage did not improve clinical outcomes in the population. The usage of smartphone apps in assisting with mental health medications adherence is still in its infancy due to lack of an evidence-based approach and the need for cocreation with patients, which might increase the impact on medication nonadherence. The lack of social cognition models in ensuring patients’ education, motivation, skills, beliefs, and type of adherence while developing the apps makes it very challenging to use in mental health interventions.18 A systematic review of 13 articles assessing the studies that investigated these apps showed a lack of standardized measures of adherence.19

Finally, another approach that could be beneficial is telepsychiatry. A recent systematic review including 17 articles showed that telemedicine improved medication adherence in patients with depression, bipolar disorder, or schizophrenia.20 Telemedicine, such as telephone call and text messaging intervention, has been shown to improve medication adherence in patients with severe mental illnesses,21 but not much research has been done to see if it can help patients with CUD. However, a randomized controlled trial found that using text messages as reminders may contribute to improving medication adherence in patients with comorbid depression and substance use.22 More research needs to explore patients with mental health conditions and comorbid cannabis use disorder, given the impact of cannabis on medication adherence.

Concluding Thoughts

Treating mental illness when patients are medication-nonadherent in the context of cannabis use is a complex process. Choosing the right intervention is important, as psychopharmacology, MI, CBT, telepsychiatry, and smartphone app interventions each pose their own individual challenges. In addition, factors that also influence medication adherence in CUD such as treatment modalities, self-motivation to treatment, self-coping capacity, and social support to influence changing behavior are things to consider when hoping for change.

Multiple research approaches have provided evidence-based findings, including integrated and multifaceted approaches to help and support current practices, but further research is needed as current options continue to pose implementation challenges.

Dr Oladunjoye is a psychiatry resident physician in the Menninger Department of Psychiatry and Behavioral Sciences at Baylor College of Medicine in Houston, Texas. Dr Ahmed is a psychiatry resident physician in the Menninger Department of Psychiatry and Behavioral Sciences at Baylor College of Medicine in Houston, Texas. Dr Murtaza is a psychiatry resident physician in the Menninger Department of Psychiatry and Behavioral Sciences at Baylor College of Medicine in Houston, Texas. Dr Jegede is an attending physician and assistant professor of psychiatry at Yale School of Medicine in New Haven, Connecticut.

If you're interested in hearing more about cannabis, there's still time to register for the 2022 Annual Psychiatric Times™ World CME Conference.


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