Does anonymity increase the reporting of mental health symptoms?

BACKGROUND: There is no doubt that the perceived stigma of having a mental disorder acts as a barrier to help seeking. It is possible that personnel may be reluctant to admit to symptoms suggestive of poor mental health when such data can be linked to them, even if their personal details are only used to help them access further care. This may be particularly relevant because individuals who have a mental health problem are more likely to experience barriers to care and hold stigmatizing beliefs. If that is the case, then mental health screening programmers may not be effective in detecting those most in need of care. We aimed to compare mental health symptom reporting when using an anonymous versus identifiable questionnaire among UK military personnel on deployment in Iraq. METHODS: Survey among UK military personnel using two questionnaires, one was anonymous (n = 315) and one collected contact details (i.e. identifiable, n = 296). Distribution was by alternate allocation. Data were collected in Iraq during January-February 2009. RESULTS: No significant difference in the reporting of symptoms of common mental disorders was found (18.1% of identifiable vs. 22.9% of anonymous participants). UK military personnel were more likely to report sub-threshold and probable PTSD when completing questionnaires anonymously (sub-threshold PTSD: 2.4% of identifiable vs. 5.8% of anonymous participants; probable PTSD: 1.7% of identifiable vs. 4.8% of anonymous participants). Of the 11 barriers to care and perceived social stigma statements considered, those completing the anonymous questionnaire compared to those completing the identifiable questionnaire were more likely to endorse three statements: "leaders discourage the use of mental health services" (9.3% vs. 4.6%), "it would be too embarrassing" (41.6% vs. 32.5%) and "I would be seen as weak" (46.6% vs. 34.2%). CONCLUSIONS: We found a significant effect on the reporting of sub-threshold and probable PTSD and certain stigmatizing beliefs (but not common mental disorders) when using an anonymous compared to identifiable questionnaire, with the anonymous questionnaire resulting in a higher prevalence of PTSD and increased reporting of three stigmatizing beliefs. This has implications for the conduct of mental health screening and research in the US and UK military.