BackgroundConcerns have been expressed about the impact that screening for risk of suicide may have on a person's mental health.AimsTo examine whether screening for suicidal ideation among people who attend primary care services and have signs of depression increases the short-term incidence of feeling that life is not worth living.MethodIn a multicentre, single-blind, randomised controlled trial, 443 patients in four general practices were randomised to screening for suicidal ideation or control questions on health and lifestyle (trial registration: ISRCTN84692657). The primary outcome was thinking that life is not worth living measured 10–14 days after randomisation. Secondary outcome measures comprised other aspects of suicidal ideation and behaviour.ResultsA total of 443 participants were randomised to early (n = 230) or delayed screening (n = 213). Their mean age was 48.5 years (s.d. = 18.4, range 16–92) and 137 (30.9%) were male. The adjusted odds of experiencing thoughts that life was not worth living at follow-up among those randomised to early compared with delayed screening was 0.88 (95% CI 0.66–1.18). Differences in secondary outcomes between the two groups were not seen. Among those randomised to early screening, 37 people (22.3%) reported thinking about taking their life at baseline and 24 (14.6%) that they had this thought 2 weeks later.ConclusionsScreening for suicidal ideation in primary care among people who have signs of depression does not appear to induce feelings that life is not worth living.