Background: Around 6 % of the Danish population suffers from a functional disorder (also called bodily distress disorder). These patients often go through a long-term diagnostic process in order to rule out structural diseases. This is a large expense for society and exhausting for the patients. Treating this group is a challenge for the Danish healthcare system. Some patients are cured, but the general practitioner is often only able to teach patients to cope with their symptoms, rather than treat and remove them. Allan Abbass has proposed intensive short-term dynamic psychotherapy (ISTDP) as an alternative treatment for functional disorders. Aim: To examine to what degree ISTDP is able to contribute to the present Danish medical understanding and treatment of functional disorders. Theoretical Basis: this master’s thesis compares two positions of understanding and treatment for functional disorders; the current treatment in Denmark and ISTDP. The current treatment is presented through work by Per Fink, who advocates for the TERM-model and techniques from cognitive behavioral therapy. ISTDP is then presented as an alternative approach, based on work by Allan Abbass. Data Sources: a systematic review of the cost effectiveness and possible symptom reduction of ISTDP in the treatment of functional disorders was performed using PsycNet and PubMed in April-May 2020. The search terms included 24 words for functional disorders, including: psychosomatic, psychophysiological disorder, medically unexplained, somatisation, fibromyalgia, pain and headache. Review Methods: the inclusion criteria were quantitative studies that examined ISTDP in adults with various forms of functional disorders or somatic symptoms. A backward search was performed on previous systematic reviews on the subject. Risk of bias were assessed. Review Results: 11 studies were included in the review, 4 of these were RCT-studies, and the remaining 7 were pre-post studies, with a total sample of 2,108 participants. Quality assessment showed low to moderate risk of bias but did not account for the lack of comparison groups throughout the studies. Two of the RCT-studies themselves did not have proper control groups. Study results showed positive results in all 11 studies. 10 studies measured symptoms and found a significant reduction, with most studies reporting moderate to large effect sizes. 1 study reported significant drop in emergency department return visits. 3 out of 5 cost effectiveness studies reported statistical data and found a significant reduction in health care costs, the reduction in cost for the last two studies were reported in percent or Canadian dollars. Thesis Discussion: the aim of the discussion was to identify limits within the presented theories and the methodical limits of this thesis. Furthermore, it’s discussed to what degree ISTDP can contribute to the present treatment both in terms of theoretical understanding and in terms of treatment supplementations to current practices when dealing with functional disorders. Conclusion: it is suggested, that ISTDP can contribute in the theoretical understanding of functional disorder, so that the unconscious and the power it has to create symptoms as defense mechanisms is acknowledged. Furthermore, it is suggested that possible attachment traumas should be covered in treatment, especially in the more severe and chronic cases of functional disorders. It is concluded that this group of patients could benefit from ISTDP. However, the evidence does not yet support a recommendation for ISTDP as an option for referral in the Danish health care system, due to the lack of RCT-studies. Still, the 11 included studies had a large sample, and all showed a positive effect of ISTDP for functional disorders, which suggests a strong therapeutic potential. Therefore, it is recommended to complete more high quality RCT-studies, and especially more Danish studies should be requested. Language: This paper is written in Danish.