The Halo Effect of Adherence to Antidepressants

Medication Adherence Patient Adherence Patient Outcomes

In the popular imagination, depression is chronic sadness. In reality, it is a devastating illness with widespread mental and physical health effects. One of the most common challenges of depression is a motivation deficit. People with depression can struggle to garner the motivation to engage in necessary activities such self-care, intensifying their symptoms. This lack of motivation can also make it difficult to adopt lifestyle changes that treat depression, such as getting more exercise or attending therapy.

It should come as no surprise, then, that motivation deficits can make depression medication adherence difficult. At least 50 percent of people with depression have poor adherence to their medications. This poor adherence can extend to other medications, triggering a cascade of preventable health symptoms.

Depression remains one of the most common chronic illnesses. It is the leading cause of disability worldwide. It is also highly treatable, yet many patients either do not seek or do not adhere to treatment. Medicare costs for patients with a history of depression are more than double that of those with no depression history.

AllazoHealth personalizes interventions to encourage medication initiation and adherence. As part of that effort, we conducted a study to examine the “antidepressant halo effect,” which suggests that antidepressant adherence also improves adherence with other medications.

AllazoHealth Studies Depression Medication Adherence Halo Effect

To examine the relationship between antidepressants and other medication adherence, we analyzed historical data across a population of approximately 45,000 Medicare Advantage Part D participants. The objective was to better understand the relationship between patient adherence to antidepressants and the three major medication classes impacting Medicare STAR ratings: oral anti-diabetics, RAS antagonists, and statins.

We defined medication adherence as achieving an 80 percent or greater proportion of days covered (PDC). According to the Pharmacy Quality Alliance, clinical evidence provides support for a standard PDC threshold of 80 percent.

How Antidepressant Compliance Extends to Other Drugs

Our results point to a clear halo effect. The largest impact was on statin compliance, with patient adherence to antidepressant medications increasing statin adherence by 33 percent. The figure for oral anti-diabetics and RAS antagonists was 28 percent.

A reverse of this trend is also true. Patients whose antidepressant medication adherence decreased also decreased adherence with other medications. This hints at depression’s role in worsening medical conditions and shows that antidepressant noncompliance may be a key driver of healthcare costs.


Although the data did not establish a causal connection, it further supports the frequently observed connection between depression and medication adherence, and between depression and worsening health. The data suggest that supporting patients to become adherent with antidepressants may help them adhere to other drug regimens, ultimately improving their quality of life and reducing avoidable healthcare costs.

Many factors play a role in antidepressant non-adherence, including:

  • Misconceptions about the disease, including the mistaken belief that depression is not chronic or that feeling better means it is gone
  • Forgetfulness
  • Comorbidities that affect cognition or the ability to be adherent
  • Medication side effects
  • Sociocultural factors, including family support and beliefs about depression
  • Physician-patient communications, especially when a physician does not fully educate a patient about depression

Addressing these factors can improve patient engagement and outcomes. AllazoHealth develops AI-enabled personalized interventions to support the most vulnerable patients and improve medication adherence.

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