The relationship between self-reported and registry-based data on use of psychoactive medications in postmenopausal women

Self-report is commonly used as a source for information regarding medication exposure in epidemiological studies. This type of data is dependent on memory and maybe vulnerable to recall bias, but also unwillingness to report may play a role. Thus, for valid results, accurate information or at least knowledge of the degree of misreports is needed. The validity of self-reported medication use can be assessed by comparing self-reports to other data sources such as pharmacy data or medical records. Previous studies have investigated several different groups of medications [1‐10]. For example, Klungel et al.[10] reported that approximately 70% of all medications currently used by patients with hypertension were correctly recalled in a self-administered questionnaire. However, the validity of self-reports has been found to vary extensively according to the type of medication taken [9, 11‐13]. The use of psychoactive medication has been shown to be less accurately reported than other medications [9, 11, 13].

Depression is one of the leading causes of disease burden in the world and a major public health problem also among the elderly [14]. The occurrence of depression is higher in women than men and its incidence peaks again after menopause [15]. There is limited validation data focusing solely [16‐19] or among others [9, 11‐13, 20‐22] on the use of antidepressants or other psychoactive agents. Especially large cohort studies are rare [13, 22]. Only few studies have investigated factors affecting accuracy of self-reported use of these medications [16, 22]. Thus, more knowledge is needed regarding the extent and reasons associated with non-reporting of psychoactive medications, which could serve as a guide for future research.

The aim of the present study is to investigate among postmenopausal women from Eastern Finland, the agreement between self-reported use and registry-based data on purchased psychoactive medications, with particular reference to antidepressants. The causes for non-reports will also be investigated.

Postmenopausal women are at increased risk of depression. This study investigated agreement between self-reported use of psychoactive medication and the National prescription register data and possible related factors among postmenopausal women. The sensitivity of self-report was 44% for any psychoactive medication and 55% for antidepressants, while it was over 80% for diuretics. However, higher use and history of work disability pension due to psychiatric cause increased sensitivity strongly.

Methodological differences such as selected golden standard, interview vs. enquiry method or structure and wording of questions might be reasons for the differences in the results between studies. Other Finnish studies have previously found high overall agreement (ad 0.87) for antidepressants [18, 19] and antipsychotics [18, 19, 22] with the same golden standard as in this study. This agreement difference might be due to longer purchase time window [18, 22], younger population [18, 22] or the interview vs. enquiry method and prescriptions brought to the interview [18, 19]. A large study by Nielsen et al.[13] with home interview but pharmacy records as a reference, found self-report sensitivity of antidepressant use (56%) similar to ours. Also Boudreau et al. [9] found lower sensitivity for antidepressants (44-66%) when using interview with specific medication questions. However, higher sensitivities for self-report of antidepressants and psychoactive medication (70-89%) have generally been obtained with different methodologies; such as medical records [12] or physician-reported data as golden standard [16], when asked “never/ever” use [16] or a direct question on medication use [17, 21] or when prescriptions were brought to the interview [18]. On the other hand, Nielsen et al.[13] also found low sensitivity for psycholeptics (38%) and especially for hypnotics and sedatives (27%). Thus, the low sensitivity in our study (29%) for the group of other psychoactive medication might be due to the high proportion of users of hypnotics and sedatives in our study sample. Similar to our study, moderate overall agreement (>0.50) for psycholeptics [13] (vs. psychoactive medication) and even better for antidepressants reporting [12, 13, 16, 17, 22] has been shown by others.

In the present study, users of psychoactive medication showed lower sensitivity for diuretics than non-users, but they reported the use of diuretics better than the use of psychoactive medication. Also in previous studies, the use of psychoactive medication has been less accurately reported than other medications [9, 11, 13]. Interestingly, however, a lower sensitivity in respect to psychoactive medication in this study was linearly related to less severe psychiatric problems (i.e. no work disability pension due to psychiatric cause) and lower use of psychoactive medication. One explanation may simply be that psychoactive medicines such as hypnotics are not used as regularly as diuretics. One might just not feel that occasional use is important enough to be mentioned in a questionnaire or the medicine may not be used at the moment or at all after purchase. Lin et al.[32] found that 28% of patients discontinued their antidepressant medication during the first month of therapy and 44% by the third month of therapy. Longer and regular use may increase recall or reduce self-perceived shame or unwillingness to report the use [10, 11, 16, 33].

In Finland the use of antidepressants doubled between 1999–2009 [34], which might decrease the unwillingness to report use of medication. However, our study subjects increased less their use of antidepressants between 1999–2009 and the sensitivity of self-report of antidepressants in 2009 was similar to that in 1999 (data not shown). It seems that regular use of antidepressants and/or long-term severe mental illness (as indicated by work disability pension) are the most important correlates of sufficient self-report.

In general, several factors may affect the agreement between self-reports and register-based data. Obesity has been previously positively associated with agreement when self-reports have been compared to medical records [12], but higher BMI is associated also with depression [35]. Thus, after including the amount of antidepressants or psychoactive medication (model 2), the significance of BMI in respect to sensitivity disappeared. Lower income [5, 16] and education level [3, 5, 10, 22] have been associated with poorer agreement, but Sjahid et al.[6] found no differences according to educational or socio-economic status. Homogeneity of our cohort may have played a role in some of the factors. In our female sample, only a small number of women had a higher education, which may have contributed to the non-significance of education. Older age has [11, 36] or has not [6] been associated with decreased validity of self-reports, while narrow age window in our study (57–68 years) might explain the found minimal age effect. In this study, being single was associated with the highest sensitivity in reporting psychoactive medication use, while in another Finnish cohort born in 1966 [22] the same was true for the married subjects. Lastly, even if Van den Brandt et al.[11] study suggested a decrease in recall along with increasing number of prescribed medications, in our study higher number of any prescribed medication currently in use was associated with better sensitivity. Stability of disease status indicated by history of work disability pension and amount of psychoactive medication in our study seemed to be more important positive determinants of agreement than putative (negative) effects of mental disease or its medication.

The strengths of this study include a large population-based cohort, high response rate and utilization of the National prescription register, which has a coverage of 97% and ability to detect also slight (i.e. irregular) use [31]. The narrow age range increased the homogeneity of the sample, but provides data on important period around retirement. Lastly, our results apply to postmenopausal women, a risk group for depression, and a base for future growing elderly population. Our method of asking current use of any prescribed medications may give lower agreement when compared to the results obtained by never-ever -type questions. Since the prescription register as a reference indicates only the medication purchased and not the actual use, it possesses a possibility to non-agreement, but this inaccuracy was minimized by checking also purchase of medication after enquiry.

Less than half of the women reported their use of any psychoactive medication and just over half their use of antidepressants compared to register-based data on purchased medication. The sensitivity of self-report increased considerably with higher use, with a history of work disability pension due to psychiatric cause or when occasional use was excluded. In conclusion, for research purposes, self-reported current medication use seems in general to be a sufficient indicator of regular use of antidepressants or in respect of use of any psychoactive medication, for those with severe psychiatric disease. However, prescription register data is more reliable for those using these medications irregularly and with less severe mental disorders.