In a typical mindfulness meditation session, a person sits on the floor, eyes closed, back straight and legs crossed, his body positioned to facilitate his inner experiences. For 10 to 15 minutes, he observes his thoughts as if he were an outsider looking in. He pays particular attention to his breathing, and when his mind wanders to other thoughts, he brings his attention back to his breath. As he practices, his mind empties of thoughts, and he becomes calmer and more peaceful.

Meditation has long been used for spiritual growth. More recently, in psychotherapy, researchers and practitioners have demonstrated interest in a type of Buddhist meditation designed to foster mindfulness, a state of being engaged in the moment without judgment. Mindfulness meditation has shown promise in treating disorders ranging from pain to psoriasis [see “Being in the Now,” by Amishi P. Jha; Scientific American Mind, March/April 2013]. But when it comes to treating diagnosed mental disorders, the evidence that mindfulness helps is decidedly mixed, with the strongest data pointing toward its ability to reduce clinical depression and prevent relapses. In this column, we will discuss these findings and some of the controversies regarding applications of mindfulness.

Openness and Acceptance

People have practiced meditation throughout history. It has evolved into many forms and is found in virtually every major religion. In 2004 psychologist Scott Bishop, then at the University of Toronto, and his associates defined mindfulness as maintaining attention on present experiences and adopting an attitude toward them characterized by curiosity, openness and acceptance.

Psychotherapy researchers have developed and evaluated variations of mindfulness for therapeutic purposes. For example, mindfulness-based stress reduction acts, as the name suggests, to reduce psychological stress. Mindfulness-based cognitive therapy, on the other hand, integrates mindfulness with methods designed to change the dysfunctional thoughts that may contribute to problematic emotions and behaviors. Both are usually delivered through eight weekly classes and an all-day workshop.

As a remedy for depression and anxiety, mindfulness meditation may help patients let go of negative thoughts instead of obsessing over them. Training people to experience the present, rather than reviewing the past or contemplating the future, may help keep the mind out of a depressive or anxious loop.

Indeed, some support exists for the efficacy of such training in ameliorating symptoms of depression and possibly anxiety. In a 2010 meta-analysis (quantitative review), psychologist Stefan Hofmann of Boston University and his colleagues examined studies that tested both forms of mindfulness meditation as a remedy for anxiety disorders and depression. They found that the meditation sessions led to significant improvements in both conditions immediately after therapy, as well as approximately three months later. Given the relatively small number of well-designed studies available at that time, however, the authors were appropriately cautious in their conclusions.

Still, a 2013 meta-analysis partly backs up the 2010 assessment. In that review, psychologist Bassam Khoury, then at the University of Montreal, and his colleagues found that both types of mindfulness-based therapies were effective for depression and anxiety disorders, though not more so than cognitive therapy without mindfulness.

Mindfulness has fared less well as a therapy for anxiety disorders in some studies. In another meta-analysis published this year, psychologist Clara Strauss of the University of Sussex in England and her associates found that mindfulness treatments were effective for depression but not for anxiety disorders. The results for anxiety may differ across investigations for various reasons, but one possibility points to differences in patient populations. For instance, some studies include individuals afflicted with anxiety disorders who also have significant health problems such as cancer, whereas others do not. How well mindfulness works may depend somewhat on the source of a patient's anxiety.

Averting Relapse

The clearest mental health benefit for mindfulness may be in reducing relapse rates for a subset of individuals with depression. Preventing relapse is a crucial challenge for therapists because relapse rates for clinical depression are extremely high. Up to 60 percent of those who have had one depressive episode will have one or more additional ones; for those who have already relapsed once, 60 to 90 percent will have further episodes; and for those who have experienced three or more depressive episodes, 95 percent will relapse.

Mindfulness seems to be particularly potent as a preventive in patients who have relapsed three or more times. In a pioneering study of mindfulness-based cognitive therapy for depression recurrence, published in 2000, psychologist John Teasdale, then at the Medical Research Council (MRC) in Cambridge, England, and his colleagues compared individuals receiving treatment as usual, such as visits to family doctors, psychiatrists and therapists, with those who also received mindfulness-based cognitive therapy. Subjects were followed for more than a year. Among those who had experienced three or more episodes of depression, mindfulness therapy significantly reduced relapse rates compared with the usual treatment. No difference between the groups emerged, however, for people who had experienced two or fewer depressive episodes. These surprising results have been replicated in several studies.

Although no one knows precisely why the benefits of mindfulness would be greater for the sample of three or more, a 2004 replication by Teasdale and psychologist S. Helen Ma, then also at the MRC, provides some leads. The researchers found, as Teasdale had previously, that in individuals who had experienced two or fewer depressive episodes, adverse life events, such as a death in the family or a relationship breakup, were a common trigger for relapse but that such external occurrences were less often associated with relapse in those who became depressed more than twice. The researchers speculated that by the time a person has had three or more depressive episodes, a significant negative event is not necessary for relapse. Instead a strong association has been formed in the mind between more ordinary negative moods and depressive thoughts. When a person who has recovered from depression experiences a mild negative mood, that mood may activate thoughts such as “Here it comes again,” triggering a full-blown depressive episode. In those cases, mindfulness might help break the cycle by enabling individuals to be less affected by fleeting unhappy thoughts so that they do not lead to emotional turmoil.

Through such mechanisms, mindfulness-based cognitive therapy and mindfulness-based stress reduction hold promise as remedies for depression and possibly anxiety. What is more, mindfulness-based cognitive therapy offers clear advantages for preventing relapse in patients who have had more than two episodes of depression. (Its ability to avert relapse for anxiety disorders is unknown.) No one fully understands how, or to what extent, mindfulness-based treatments contribute to recovery in these illnesses. Nevertheless, such treatments constitute an exciting new direction in psychotherapy.