Complementary and alternative medicine (CAM) has been largely ignored by health economists as an area of research. That fact is possibly related to the low esteem of CAM in the medical profession.
Defining CAM is difficult, because the field is very broad and constantly changing. According to the National Center for Complementary and Alternative Medicine (NCCAM), CAM is a group of diverse medical and healthcare systems, practices, and products that are not generally considered part of conventional medicine . The Cochrane Collaboration definition of complementary medicine is that it includes all such practices and ideas that are outside the domain of conventional medicine in several countries and defined by its users as preventing or treating illness, or promoting health and well-being. These practices complement mainstream medicine by satisfying a demand not met by conventional practices and diversifying the conceptual framework of medicine .
Patients around the globe are increasingly embracing CAM as a contributor to health. A recent study by the US National Institute of Health shows that 4 out of 10 Americans used some form of CAM in 2007. Another study on Switzerland reported that almost 11% of the population had used one of five CAM streams (anthroposophic medicine, homeopathy, neural therapy, phytotherapy, and Traditional Chinese Medicine) in 2002. The CAM doctors in that study treated patients that tended to be younger, female, and better educated. These patients also tended to have a favorable attitude toward complementary medicine and to exhibit chronic and more severe forms of disease. The majority of alternative medicine users appear to have chosen CAM mainly because they wish to undergo a certain procedure; additional reasons include desire for more comprehensive treatment and expectation of fewer side effects . In a referendum in Switzerland in 2009, two-thirds of the voters were in favor of a wider coverage of CAM by public health insurance. In January 2011, based on the positive outcome of a national referendum, the Swiss authorities decided that five main streams of CAM (anthroposophic medicine, homeopathy, neural therapy, phytotherapy, and Traditional Chinese Medicine) will be covered by the mandatory health insurance for a period of 6 years (2012–2017) .
In many cases, the effectiveness of CAM has not been proven in clinical trials . However, lack of proof of effectiveness is obviously not the same as proof of ineffectiveness. Clearly, the status of a treatment can change from CAM into conventional medicine once scientific evidence on effectiveness becomes available. Two examples of CAM treatments that have become (more) accepted by conventional medicine are St. John’s wort and acupuncture for specific indications. St. John’s wort, for more than 90 years used in anthroposophic medicine, has become part of the conventional guidelines for the treatment of depression, based on scientific evidence from randomized controlled trials . Hopton and McPherson  conclude on the basis of a systematic review of pooled data from meta-analyses that acupuncture is more than a placebo for commonly occurring chronic pain conditions. In addition, in her thesis, van den Berg  recently demonstrated positive effects of acupuncture on obstetric health problems (breech presentation). Also, Servan-Schreiber  presents a series of recent examples of the transition from CAM to conventional medicine in depression treatment. Some of the methods described by Servan-Schreiber have been practiced for centuries, cannot be patented, and are available at low costs. These findings underscore the fact that methods that are considered CAM today could be effective and have a large cost-saving potential.
Anthroposophic medicine, acupuncture, and homeopathy are three main streams of CAM. One of the core features of CAM is its orientation on preventative and curative health promotion as an additional approach to a more conventional fighting disease approach. Anthroposophic medicine is an integrative diagnosis and therapy concept, developed from 1921 onwards and practiced today in over 60 countries. It combines mainstream scientific medicine with Rudolf Steiner’s anthroposophy. Anthroposophic medicine considers a human being as a whole entity—body, mind, soul, and individuality. It aims to stimulate the self-healing forces of the body, restoring the balance of bodily functions, and strengthening the immune system, rather than primarily relieve the symptoms of disease. Specific anthroposophic approaches include anthroposophic medicinal products, massage therapy, art and music therapy, and speech and movement therapies .
Homeopathy is a form of alternative medicine, first proposed by the German physician Samuel Hahnemann in 1796, that attempts to treat patients with heavily diluted substances. These substances that cause certain symptoms in healthy individuals are given as the treatment for patients exhibiting similar symptoms. The appropriate homeopathic medicinal product aims to stimulate the body’s inherent forces of self-recovery .
Acupuncture is one of the main forms of treatment in Traditional Chinese Medicine (TCM). It involves the use of sharp, thin needles that are inserted in the body at very specific points. This process is believed to adjust and alter the body’s energy flow into healthier patterns and is used to treat a wide variety of illnesses and health conditions .
In their review, Herman et al.  report that some studies indicate that CAM therapies may be considered cost-effective compared with usual care for various conditions: acupuncture for migraine, manual therapy for neck pain, spa therapy for Parkinson’s, self-administered stress management for cancer patients undergoing chemotherapy, preoperative and postoperative oral nutritional supplementation for lower gastrointestinal tract surgery, biofeedback for patients with ‘functional’ disorders (e.g., irritable bowel syndrome), and guided imagery, relaxation therapy, and potassium-rich diet for cardiac patients. A systematic review of randomized clinical trials on the use of so-called natural health products shows evidence of cost-effectiveness in relation to postoperative surgery but not with respect to the other conditions assessed . Studer and Busato  demonstrated that general practitioners who have completed certified additional training in CAM after obtaining their conventional medical degree (GP-CAMs) (n = 257) compared with general practitioners who have not (GPs) (n = 174) have equal costs per patient per year, but significantly lower costs per doctor (29%) per year, although GP-CAMs take more time per patient. A NCCAM study in 2007 demonstrated that CAM costs were 11.2% of total out-of-pocket expenditures on healthcare in the USA .
GP care varies between European countries in terms of structure, working methods, and responsibilities. In the Netherlands, GPs are the central gatekeepers for reference to the rest of healthcare, like specialists and paramedics. Dutch general practitioners generally receive a quarterly fixed fee per patient plus a fee-for-service per consultation and per drug prescription. There is no difference between the financial incentives faced by GPs and GP-CAMs. In the Netherlands, purchasing basic health insurance is mandatory for all citizens. In addition, citizens are free to purchase supplementary insurance.
Since there is a lack of cost-effectiveness data of CAM in the Netherlands, in this paper, we compare the performance of general practitioners who have completed certified additional training in CAM after obtaining their conventional medical degree (GP-CAMs) with general practitioners who have not (GPs). More specifically, we consider GP-CAMs with additional training in anthroposophic medicine, homeopathy, or acupuncture (about 1% of GPs for each of these CAM types).