- age—adherent patients were significantly older than nonadherent (P=.01)
- race—whites were more adherent than nonwhites (67% vs 0%; P=.001)
- gender—men were more adherent than women (81% vs 56 %; P=.03)
- depression severity—adherent patients had milder depressive symptoms than nonadherent patients (P=.04).
When percentage of days with correct intake and timing was examined, depressive severity was the only variable that differentiated adherent from nonadherent patients. Individuals who had at least 80% adherence over the first 3 months initially presented with milder depressive symptoms at the baseline evaluation (P=.02). Other demographic and clinical characteristics did not differentiate adherent from nonadherent patients.
Regimen duration discussions linked to better adherence
Several key messages about antidepressant medication differentiated adherent from nonadherent patients (TABLE 3). For percentage of prescribed doses taken during a 90-day period, the key messages differentiating adherent from nonadherent patients were “told what to do if there were questions,” “keep taking the medication even if feeling better,” and “told how long to expect to take medicine.”
For the more stringent measure of adherence (percentage of days with correct intake and timing), 4 key messages differentiated adherent from nonadherent patients: “told what to do if there were questions,” “told how long to expect to take medicine,” “advised of how long side effects will last,” and “given advice on managing minor side effects.”
TABLE 3
3-month adherence among patients receiving specific patient education at baseline (N=178)
| PATIENTS RECEIVING DISCUSSION | ADHERENCE (YES ≥80%) | ||||||
|---|---|---|---|---|---|---|---|
| DOSES TAKEN OVER 3 MONTHS (%) | DAYS WITH CORRECT INTAKE AND TIMING OVER 3 MONTHS (%) | ||||||
| EDUCATION ITEM | % (N) | NO | YES | P | NO | YES | P |
| Take on a daily basis | 79.2 (152) | 75.0 | 83.1 | .23 | 77.8 | 80.5 | .72 |
| Told how long medication would take to work | 75.5 (145) | 69.0 | 81.5 | .08 | 70.4 | 85.4 | .06 |
| Told what to do if there were questions | 75.5 (145) | 66.7 | 86.2 | .006 | 70.4 | 87.8 | .03 |
| Asked about prior use of similar medicine | 71.4 (137) | 71.4 | 73.8 | .74 | 72.2 | 73.2 | .91 |
| Don’t stop taking without checking with office | 63.0 (121) | 56.0 | 69.2 | .10 | 57.4 | 73.2 | .08 |
| Given simple explanation of how medicine works | 59.4 (114) | 54.8 | 63.1 | .31 | 55.6 | 65.9 | .26 |
| Keep taking even if feeling better | 58.9 (113) | 48.8 | 64.6 | .05 | 51.9 | 65.9 | .12 |
| Discussed common side effects | 46.9 (90) | 41.7 | 47.7 | .46 | 40.7 | 53.7 | .16 |
| Advised on what to do if there are major side effects | 30.2 (58) | 28.6 | 29.2 | .93 | 25.0 | 39.0 | .09 |
| Told how long to expect to take this medicine | 29.2 (56) | 16.7 | 38.5 | .003 | 20.4 | 41.5 | .009 |
| Advised of how long side effects will last | 28.6 (55) | 23.8 | 32.3 | .25 | 22.2 | 41.5 | .02 |
| Given advice on managing minor side effects | 27.1 (52) | 23.8 | 30.8 | .34 | 21.3 | 41.5 | .01 |
Multivariate predictors of adherence
3 Key issues emerge
Multivariate hierarchical logistic regression was used to examine the association between the binary outcome of adherence to antidepressants over a 3-month period (adherent vs nonadherent), significant patient characteristics, and patient recall of physician messages about antidepressant use. Two key physician messages—“told how long to expect to take the medicine” and “told what to do if there were questions”—distinguished between patients who took at least 80% of the prescribed medication doses and those who did not. The odds of being adherent to the regimen more than tripled among those who said they had received these 2 messages when compared to those who said they had not (OR=3.8; 95% CI, 1.6–8.9; OR=3.8; 95% CI, 1.4–10.4) (TABLE 4).
One message was associated with adherence based on the percentage of days with correct intake and timing. The odds of being adherent more than doubled among patients who reported that they were “told how long to expect to take the medicine” compared with those who said they had not been told (OR=2.6; 95% CI, 1.1–5.9) (TABLE 5). Models testing for interactions of multiple messages were nonsignificant.
Discussion
Physician messages tied to adherence
Consistent with prior reports,4 we found a significant decrease in adherence to prescribed antidepressants during the first 3 months of treatment. However, physicians’ educational messages about how to take the antidepressant were significantly associated with adherence in both univariate and multivariate analyses.
While more than three-quarters of study participants indicated that they were told to take the medication daily, how long it would take to work, and what to do if there were questions, the least frequently reported messages involved managing side effects, with less than a third of patients indicating that their physician had discussed this with them. The latter finding is important because univariate analyses indicated that discussion of side effects was significantly associated with future adherence during the first 3 months of treatment.
In multivariate analyses, we were able to further identify those key messages that were associated with at least 80% adherence over a 3-month period. A unique aspect of our study is the use of electronic monitoring to measure adherence, which provides detailed information on the exact time patients took their medication and allowed us to identify predictors associated with more conservative (percentage of days with correct intake and timing) and less conservative (percentage of prescribed doses taken) measures of adherence. Our findings suggest that primary care physicians may be able to improve adherence by providing simple and specific information about using antidepressants. The most important of these being “how long to expect to take the medicine” and “what to do if there are questions.”