How well do our current treatments for depression work?
Depression is a major global health challenge. It is a highly prevalent, chronic, disabling, and recurrent disorder, with enormous individual, societal, and economic burden. It is estimated that approximately 10-20% of all people will experience at least one episode of clinical depression during their lifetime. Depression ranks highest among all the disorders responsible for global disease burden, as defined by years of health lost to disease. Moreover, people who have had depression tend to multiple episodes of depression, and it has impact on all aspects of their lives, including increasing their risk of developing certain phsycial health problems.
It therefore seems opportune to stop and consider how well the mental health and medical professions (GPs, psychologists, psychiatrists, nurses, etc) are doing at treating and reducing depression.
We can start by reviewing how well our treatments work. How good are they are reducing the symptoms of depression and helping people to stay well? How efficacious are they?
Our current best treatments for depression, with the most comprehensive evidence, are antidepressant medications and structured forms of psychotherapy such as cognitive-behavioural therapy (CBT) and interpersonal therapy. All of these treatments have been shown to have good efficacy in randomized controlled trials, outperforming no treatment or placebo controls. Indeed, recovery rates for these treatments are better than for many treatments for physical conditions. So we do have treatments that work for depression.
Nonetheless, reviews of the field indicate that these treatments still have significant limitations, with considerable scope for improvement. A substantial proportion of patients, around 40%, show only partial or no response to treatment, whether it be medication or psychotherapy. Only about a third of patients achieve remission – the reduction of symptoms to a normal healthy level. A good number of people are thus not substantially benefited by the treatment they receive. Some people will benefit from another treatment but we don’t which is the best treatment to try for any individual person, relying on trial and error to select interventions. We therefore need to improve the strength and efficacy of treatments and to find more systematic approaches to matching the best treatment to each individual patient.
Further, even for those patients who do respond well to treatment, long-term benefit is limited. Of those improving between 50-80% will have a relapse or a recurrence of depression within the next year, and there is limited sustained recovery. CBT has been shown to reduce the risk of relapse and recurrence after the course of therapy has finished but this can be significantly improved. The benefits of antidepressant medication cease once the treatment regime is discontinued. We therefore need to find ways for the benefits of treatments to persist for longer.
However, there are other major challenges in order to address the global burden of depression. Because of the high frequency and prevalence of depression, many millions of people would benefit from treatment. However, only about 40% of those in need receive an evidence-based treatment. Whilst antidepressants are widely available, many people want an alternative and are unsatisfied with the need to take medication indefinitely, often with unwanted side effects. For these reasons, adherence to antidepressants is poor, and a substantial number of people discontinue medication early.
In addition, the dominant model of psychotherapy in the form of traditional face-to-face psychotherapy can never be sufficiently widely available to meet this treatment need. Put simply, there are not enough therapists to cover the high rates of depression, and for existing models of intervention delivery, there never will be enough therapists. We thus have a major treatment gap.
In a cogent article in Perspectives in Psychological Science in 2011, Alan Kazdin and Stacey Blase of Yale University examined the need for mental health treatment and reviewed current models of delivery. They concluded that a major shift in intervention research and clinical practice is required to reduce the prevalence, incidence, and burden of mental illness. As the most common form of mental illness, their arguments are particularly pertinent to depression. They noted that considerable work needed to be done to make treatments more accessible and engaging and relevant for those experiencing mental health difficulties. Therapy needs to be more widely available, suitable for all ages, all ethnic and cultural backgrounds, and convenient to access, whatever the geographical location or working schedule of the individual sufferer.
Kazdin and Blase proposed developing a portfolio of different models of delivering treatments to address the burden of mental illness, in addition to traditional face-to-face psychotherapy. One model of delivery is the use of internet-based treatments or e-health, which have the ability to reach a large number of people and have wide coverage. Internet treatments also have the potential advantages of being accessible at anytime and anywhere there is web access, transcending space and time. Internet-based treatments can also be cost-effective, enabling large numbers of people to be treated. With technological advances, these treatments could also be provided over smart phones (m-health).
Other models of treatment delivery to increase the availability and accessibility of interventions include involving non-professionals in the provision of useful simple interventions, self-help interventions such as based around audio recordings or self-help books, the provision of mental health resources within schools and workplaces, and useful media campaigns highlighting healthy behaviors. A key element within any successful campaign to reduce the burden of depression will also need to include a focus on prevention, as well as treatment, to halt the incidence of new episodes of depression.
One barrier to developing more potent treatments is that we don’t really know how treatments work or what the active ingredients of psychological treatment for depression are. Different mechanisms of action have been proposed but none has been definitively confirmed. There is still an ongoing debate as to the extent to which therapy works through specific processes targeted in therapy (e.g., by reducing negative thinking in CBT) and/or through non-specific effects such as having a positive relationship with a therapist, who instils hope and optimism, and helps to give the patient structure.
To date, research into treatments has focused on the use of randomized controlled trials in which the psychotherapy (e.g., CBT) is compared to an existing treatment (such as medication) or no treatment. These trials are perfectly suited to evaluating a therapy and scientifically confirming whether it works as well or better than a comparison treatment. This approach has established that we have efficacious treatments that work. However, it has not significantly advanced our knowledge of how therapy works. Most therapies are what we call “complex interventions” in that they combine multiple treatment elements including different techniques, different messages, and different means of delivery, into a single treatment package. Traditional randomized controlled trials can help us to determine how one treatment package compares to another, but cannot help us to determine which of these components might be the active ingredients of therapies because they are not examined separately.
The pace of improvement of psychological treatments for depression has been slow, in part because of the exclusive focus on randomized controlled trial research, which has limited our ability to unpack the active ingredients and mechanisms of treatment. For example, CBT for Depression has essentially remained unchanged from the original and seminal treatment manual written by Aaron Beck and colleagues over 30 years ago in 1979. Within a treatment package, such as CBT for depression, there may be components that are active, components that are inert and have no effect, and even some components that may be unhelpful. Distinguishing which components have which effects would help us to systematically build stronger and briefer treatments, by only including the active ingredients. The use of innovative approaches such as factorial designs is necessary to unpack the potential effects of individual treatment components, as well as to determine if particular treatment elements interact with each other. The field needs to adopt these more innovative approaches to grasp the nettle of how to more rapidly improve our treatments for depression.