Background  Inflammatory bowel diseases are chronic conditions requiring medication throughout life to treat the disease and control the risk of relapse and colorectal cancer. Adherence to prescribed drugs is therefore crucial to their management.

Aim  To identify determinants and potential risk factors of non-adherence in inflammatory bowel disease patients.

Methods  An anonymous 24-item questionnaire (available online as Supplementary material) was administered to 485 out-patients attending a tertiary referral centre.

Results  Sixty-one per cent of the patients reportedly adhered to their treatment. No differences emerged between inflammatory bowel disease and socio-demographic characteristics other than age, non-adherence being significantly associated with cases under 40 years (43% vs. 34%, P = 0.041). The most common reasons for non-adherence vs. adherence were forgetfulness (61% vs. 44%, P = 0.000), disease remission (25% vs. 10%, P = 0.000), recent diagnosis (24% vs. 15%, P = 0.000) and full-time employment (55% vs. 26%, P = 0.000). Oral therapy was associated with a significantly better adherence than rectal therapy (60% vs. 32%, P = 0.001). Communication affects patient adherence: a significant interaction was found for adherence and patients <40 years who had a good relationship with their doctors.

Conclusions  Risk factors for non-adherence are younger age, busy working life, recent diagnosis and disease remission. Good communication with the doctor might improve adherence.