ABSTRACTObjectiveTo investigate if pre‐existing mental health morbidity (MHM) might influence help‐seeking and willingness to undergo diagnostic investigations for potential colorectal cancer (CRC) symptoms.MethodsAn online vignette survey was completed by 1307 adults aged > 50 years recruited through Prolific, a UK panel provider. Participants self‐reported any chronic physical or MHM. After having been presented with vignettes describing new onset symptoms (rectal bleeding or change in bowel habit), participants answered questions on symptom attribution and attitudes to investigations. Using multivariable logistic regression we examined the association between MHM and symptom attribution, intended help‐seeking, and willingness to undergo investigations, controlling for socio‐demographic factors and physical morbidities.ResultsSelf‐reported MHM (reported by 14% of participants) was not associated with cancer symptom attribution (29% of participants with or without MHM mentioned cancer as a possible reason for rectal bleeding and 14% for change in bowel habit). Individuals with self‐reported MHM were less likely to contact a GP if experiencing a change in bowel habit (19% vs. 39%; adjusted (a)OR = 0.34, 95% CI 0.19–0.60) and to mention rectal bleeding to their GP (83% vs. 89%, aOR = 0.49, 95% CI 0.26–0.94). Although most participants would be willing to undergo a colonoscopy for these high‐risk symptoms, those with depression/anxiety were less willing (90% vs. 96%; aOR: 0.37, 95% CI 0.16–0.87).ConclusionsIndividuals with self‐reported MHM are less likely to seek help and less willing to undergo investigations for high‐risk symptoms. Targeted support, for example, through additional mental health nurses, might facilitate prompt cancer diagnosis for the large group of people with MHM.