In our sample, 46% of psychiatric inpatients who were approached were recruited into the TOB study. On the other hand, a randomized controlled trial (RCT) of dialectical behavioural therapy on women with BPD in Netherlands reported a much higher recruitment rate of 70%. (15) In studies of other psychiatric illnesses, recruitment rates vary widely between 35% and 68%. (10, 13, 16) In terms of retention, 70% of the recruited participated remained in the TOB study. This is similar to findings from a meta-analysis of psychotherapy trials for BPD, which reported an overall retention rate of 71–75%. (17) Retention rates in trials involving other psychiatric illnesses tend to range between 40–75%. (10, 18)
Age and sex were not predictors of recruitment or retention. This is consistent with previous studies on and BPD that reported no significant association between retention and sociodemographic factors. (17) However, studies on psychotic disorders had found that younger patients are more likely to participate in research studies compared to older patients. (12, 13) In terms of clinical variables, a meta-analysis found that commitment to change, low impulsivity, and strong therapeutic relationship were predictive of retention among patients with BPD. (17) In studies of psychotic disorders, patients with higher illness severity, suicidality, longer length of hospitalization, and medical comorbidities were less likely to be approached about study participation (13) and more likely to decline participation when approached. (12)
Overall, “not interested” was the most common reason provided for declining to participate in the study. Although this is very broad explanation that can encompass many different reasons, it seemed to frequently stem from the stigma related to BPD. Potential participants frequently expressed discomfort about being associated with BPD, and were quick to emphasize that they do not have a diagnosis of BPD. This is consistent with previous findings that BPD is by far one of the most stigmatized psychiatric disorders, even within the mental health system itself. (6, 7) In fact, attitudes and behaviours of mental health workers towards BPD are even more negative than other illnesses such as schizophrenia and mood disorders. (19–21) Individuals with BPD are often perceived as “annoying” and “undeserving of sympathy” by the public. (6, 7) As a result, BPD patients experience greater levels of existential shame and self-stigma compared to those with other mental illnesses (22), and report significant discriminatory experiences. (23) Stigma is also a common barrier to participation in psychiatric studies in general. In a systematic review of this topic, Woodall et al. reported stigma and lack of acceptance of diagnosis as two of the most common barriers to research recruitment among patients with mental illness. (9) Similarly, disagreement with psychiatric diagnosis was the fourth most frequently cited barrier to recruitment, in a RCT of individuals with severe mental illness. (10)
Another potential reason behind the lack of interest in participation was that we were unable to provide participants with monetary or other forms of reimbursement for their time and effort. Similarly, the study process was quite long, and involved two hours of psychological interviewing and administration of several standardized questionnaires – a process that can feel intrusive and tiring for many patients.
In terms of study retention, there were some logistical challenges around scheduling. This issue is by no means specific to BPD or psychiatry, and is commonly encountered in all clinical trials. (9, 10, 24) In fact, the inpatient setting often allows for easier scheduling and access to participants compared to outpatient clinics. Regardless, 29–72% of the participants withdrew from our study either directly or partially due to scheduling issues.
Another major factor in recruitment and retention was the well-being of the patients. Two patients were unable to participate meaningfully in the study due to the poor state of their physical or mental health. The fact that four participants withdrew consent because they found the study process too upsetting or tiring is perhaps unsurprising, given that the study involved lengthy interviews with highly personal questions. This may also reflect the fluctuating course of most mental illnesses. In fact, illness severity and fear of exacerbating illness were two of the largest themes that arose in the systematic review by Woodall et al. (9)
Having identified these challenges, throughout the TOB study we began to implement some strategies to improve recruitment and retention. To target the stigma surrounding BPD, best efforts were made to avoid the use of stigmatizing language in explaining the study to patients. As well, the need for controls in the study was emphasized; being part of the study did not necessarily mean that the participant had BPD, as the aim of the study was to explore BPD characteristics in a random sample of psychiatric inpatients. With regards to the scheduling challenges, the study investigators communicated more closely with inpatient unit staff to avoid any scheduling conflicts. Written and verbal reminders were also used. Lastly, to make the process less tiring for participants, we offered to perform the interview in multiple shorter segments. Participants were reminded that they could pause or leave the interview at any time.
As these strategies were gradually implemented over time and not in a structured manner, we were unable to determine their effects on recruitment and retention rates. Generally, it was felt that the strategies used to target stigma were not very effective. Although patients were reassured that participation in the study did not mean that they had BPD, patients still continued to express discomfort about being associated with BPD in any way. Considering the prevalent and deep-rooted nature of the stigma surrounding BPD, there is only so much that can be done in individual studies to address it. There is a need for more concerted, large-scale efforts to address the stigma surrounding BPD, such as public awareness campaigns and psychoeducation of diagnosed patients. (7)
A recent systematic review reported on various recruitment strategies used in psychiatric research such as: travel support; avoiding stigmatizing language; and better education about the purpose and nature of the investigation. (9) However, very few of these strategies have been formally evaluated and thus their relative efficacies are unclear. (9) For instance, simply not using the term “borderline personality disorder” may in fact add to the stigma in the long run, by avoiding the clinical term of a common and serious mental illness. On the other hand, in a more recent systematic review, Liu et al. found 11 studies on recruitment and two studies on retention strategies in mental health trials. (25) Recruitment by clinical research staff and non-web-based advertisements were found to be effective in improving recruitment, while the use of abridged questionnaires and regular reminders were helpful in retention. Financial incentives were effective in improving both. (25) Outside of psychiatry, stakeholders’ advisories, personalized update letters, and educational materials have been reported as successful recruitment and retention strategies in clinical trials. (26, 27)
There are several limitations of the current study. Firstly, no data on recruitment rates were collected at the beginning of the study. We only began to collect this information after implementing several recruitment and retention strategies; thus, it’s possible that recruitment and retention were even lower previously, and that the reported values are an underestimate of the study average. Secondly, the strategies were gradually implemented over time and thus their effects on recruitment and retention could not be evaluated. Thirdly, only brief descriptions were provided by participants regarding their reason for declining consent or withdrawing from the study. Fourth, limited data were available on individuals who declined to participate, making it challenging to examine clinical predictors of recruitment. Fifth, only patients who were deemed to be suitable candidates were approached by the recruiters, introducing sampling bias. The more severely ill and agitated patients were likely left out of the study, thus underestimating the true recruitment and retention rates in this population.