We now recognise that withdrawal symptoms from antidepressants are common, and can be severe and long-lasting in some people. Many withdrawal symptoms overlap with symptoms of anxiety or depression, making it difficult to distinguish withdrawal from relapse. We describe how their onset soon after dose reduction, the association of psychological with physical symptoms, their prompt response to reinstatement, and their typical ‘wave’ pattern of onset, peak and resolution can help distinguish withdrawal symptoms from relapse. We also examine evidence that suggests that antidepressant withdrawal symptoms are misdiagnosed as relapse in discontinuation studies aimed at demonstrating the ability of antidepressants to prevent future relapse (relapse prevention properties). In these discontinuation studies people have their antidepressants stopped abruptly, or rapidly, making withdrawal symptoms very likely, and little effort is made to measure withdrawal symptoms or distinguish them from relapse. We conclude that there is currently no robust evidence for the relapse prevention properties of antidepressants, and current guidance might need to be re-evaluated.