Previous evidence has shown positive associations between post-traumatic stress disorder (PTSD) and hypertension, dyslipidaemia and diabetes mellitus, which are all risk factors for stroke, but the role of PTSD in the subsequent development of stroke is still unknown.

To investigate the temporal association between PTSD and the development of stroke.

Identified from the Taiwan National Health Insurance Research Database, 5217 individuals aged 18 years, with PTSD but with no history of stroke, and 20 868 age- and gender-matched controls were enrolled between 2002 and 2009, and followed up until the end of 2011 to identify the development of stroke.

Individuals with PTSD had an increased risk of developing any stroke (hazard ratio (HR) 3.37, 95% CI 2.44–4.67) and ischaemic stroke (HR = 3.47, 95% CI 2.23–5.39) after adjusting for demographic data and medical comorbidities. Sensitivity tests showed consistent findings (any stroke HR = 3.02, 95% CI 2.13–4.28; ischaemic stroke HR = 2.89, 95% CI 1.79–4.66) after excluding the first year of observation.

Individuals with PTSD have an increased risk of developing any stroke and ischaemic stroke. Further studies are required to investigate the underlying mechanisms.

People with major depressive disorder who fail to respond to adequate trials of antidepressant treatment may harbour hidden bipolar disorder.

We aimed to compare the rates of a change in diagnosis to bipolar disorder among people with major depressive disorder with stratified responses to antidepressants during an 8-year follow-up period.

Information on individuals with major depressive disorder identified during 2000 (cohort 2000, n = 1485) and 2003 (cohort 2003, n = 2459) were collected from a nationally representative cohort of 1 000 000 health service users in Taiwan. Participants responding well to antidepressants were compared with those showing poor responses to adequate trials of antidepressants.

In 7.6–12.1% of those with a diagnosis of unipolar major depressive disorder this diagnosis was subsequently changed to bipolar disorder, with a mean time to change of 1.89–2.98 years. Difficult-to-treat participants presented higher rates of change to a bipolar diagnosis (25.6% in cohort 2000; 26.6% in cohort 2003) than easy-to-treat participants (8.8–8.9% in cohort 2000; 6.8–8.6% in cohort 2003; P<0.0001). Regression analysis showed that the variable most strongly associated with the change in diagnosis was antidepressant use history. The difficult-to-treat participants were associated most with diagnostic changing (cohort 2000: odds ratio (OR) = 1.88 (95% CI 1.12–3.16); cohort 2003: OR = 4.94 (95% CI 2.81–8.68)).

This is the first large-scale study to report an association between antidepressant response history and subsequent change in diagnosis from major depressive disorder to bipolar disorder. Our findings support the view that a history of poor response to antidepressants in unipolar depression could be a useful predictor for bipolar diathesis.