does not treat the disease. a 2015 cochrane review found unclear usefulness for cancer pain, though other reviews have found tentative evidence of benefit. it is of unclear effect in hot flashes in people with breast cancer. the effects of aromatherapy are unclear with no peer-reviewed research in regards to cancer treatment. psychotherapy may reduce anxiety and improve quality of life as well as allow for improving patient moods. massage therapy may temporarily reduce pain. there is no evidence that cannabis has a beneficial effect in preventing or treating cancer in humans. hypnosis and meditation may improve the quality of life of cancer patients. music therapy eases cancer-related symptoms by helping with mood disturbances. alternative theories of cancer some alternative cancer treatments are based on unproven or disproven theories of how cancer begins or is sustained in the body. some common concepts are: mind-body connection this idea says that cancer progression is related to a person's mental and emotional state. treatments based on this idea are mind–body interventions. proponents say that cancer forms because the person is unhappy or stressed, or that a positive attitude can cure cancer after it has formed. a typical claim is that stress, anger, fear, or sadness depresses the immune system, whereas that love, forgiveness, confidence, and happiness cause the immune system to improve, and that this improved immune system will destroy the cancer. this belief that generally boosting the immune system's activity will kill the cancer cells is not supported by any scientific research. in fact, many cancers require the support of an active immune system (especially through inflammation) to establish the tumor microenvironment necessary for a tumor to grow. toxin theory of cancer in this idea, the body's metabolic processes are overwhelmed by normal, everyday byproducts. these byproducts, called "toxins", are said to build up in the cells and cause cancer and other diseases through a process sometimes called autointoxication or autotoxemia. treatments following this approach are usually aimed at detoxification or body cleansing, such as enemas. low activity by the immune system this claim asserts that if only the body's immune system were strong enough, it would kill the "invading" or "foreign" cancer. unfortunately, most cancer cells retain normal cell characteristics, making them appear to the immune system to be a normal part of the body. cancerous tumors also actively induce immune tolerance, which prevents the immune system from attacking them. epigenetic disregulation this claim uses research into the mechanism of epigenetics to understand how mutations in the epigenetic machinery of cells will altered histone acetylation patterns to create cancer epigenetics. dna damage appears to be the primary underlying cause of cancer. if dna repair is deficient, dna damage tends to accumulate. such excess dna damage can increase mutational errors during dna replication due to error-prone translesion synthesis. excess dna damage can also increase epigenetic alterations due to errors during dna repair. such mutations and epigenetic alterations can give rise to cancer.