LIMITATION OF SD: Systematic desensitisation is a time-consuming + economical treatment as it requires the presence of a trained professional and lasts between 6-8 sessions, this means that it might be the most economically beneficial choice for health-care providers such as the NHS who are already under financial strain. Furthermore, systematic desensitisation cannot treat all phobias, such as fear of flying, as they cannot provide the phobic stimuli as necessary thus suggesting it to be limited in applicability.