BACKGROUND: Most adults fail to achieve remission from common mental health conditions based on pharmacological treatment in primary care alone. There is no data synthesising the reasons. This review addresses this gap through a systematic review and thematic synthesis to understand adults' experiences using primary care for treatment-resistant mental health conditions (TRMHCs). We use the results to produce patient-driven recommendations for better support in primary care. METHODS: Eight databases were searched from inception to December 2020 for qualitative studies reporting research on people's experience with TRMHCs in primary care. We included the following common mental health conditions defined by NICE: anxiety, depression, panic disorder, post-traumatic stress, and obsessive-compulsive disorder. Two reviewers independently screened studies. Eligible studies were analysed using an aggregative thematic synthesis. RESULTS: Eleven studies of 4456 were eligible. From these eleven studies, 4 descriptive themes were developed to describe a cycle of care that people with TRMHCs experienced in primary care. In the first stage, people preferred to self-manage their mental health and reported barriers that prevented them from seeing a GP (e.g., stigma). People felt it necessary to see their GP only when reaching a crisis point. In the second stage, people were usually prescribed antidepressants, but were sceptical about any benefits they had to their mental health. In the third stage, people self-managed their mental health (e.g., by adjusting antidepressant dosage). The fourth stage described the reoccurrence of mental health and need to see a GP again. The high-order theme, 'breaking the cycle,' described how this cycle could be broken (e.g., continuity of care). CONCLUSIONS: People with TRMHCs and GPs could break the cycle of care by having a conversation about what to do when antidepressants fail to work. This conversation could include replacing antidepressants with psychological interventions like talking therapy or mindfulness.