“I have read on the internet about depression and if I understand it well, it is basically unknown what a depression is. So if we don’t know what depression is, is it still possible to treat it? How is that possible?”
We can see mental disorders, even if we can’t define them perfectly
It is indeed still not clear what a depression (or any other mental disorder) exactly is. There are no blood tests or any other objective tests that can say whether someone has a depression. Of course we know that depression exists, because we can see people suffering from it. But we don’t know what it is, or why one person gets it and another not in the same circumstances.
Basically, we say that someone has a depression when that person meets a number of criteria according to a list of criteria that was made by a group of experts, like in the classification systems of the DSM or ICD. But in reality it is not clear what the threshold is for having a depression or not. And it could be caused by a biological problem, a psychological problem, a social problem, or a combination of these. Science has still not established what the exact pathways are that cause depression.
You don’t need to know the cause to know what helps
But we can develop effective treatments, even though we do not know what depression is. That is because we can use so-called randomized controlled trials to examine the effects of a treatment. In such a study a group of people with depression are split into two subgroups in a random way. One subgroup gets the treatment and the other one not, but otherwise they are exactly the same. When the treatment ends and there are differences between the two subgroups, these differences can logically only be caused by the treatment.
This kind of study is the strongest design available in science to show causally if a treatment works. One does not need to understand what depression is, where it comes from, or what the causes are.
Limits of this method
This sounds simple and straightforward, but such randomized controlled trials also have all kinds of problems and it is often still not completely certain if the treatment works when a trial has shown that. But it is the best design available in science to show if something works.
If treatments are not examined in randomized trials, the uncertainty if the treatment actually works is much larger. Many problems change over time, because conditions change, things happen in the personal life of a patient, the patient learns new coping skills or a talk with a friend gives new insights about the problems. That means that if you simply examine how many people who receive a treatment get better, you never know how many would have gotten better without the treatment. Therefore randomized controlled trials are very much needed to examine the effects of treatments and there are no good alternatives for such trials.
Fortunately, there are many randomized trials examining the effects of psychotherapies, and that has resulted in a lot of knowledge about these treatments.
Even though we still do not know what a depression is…
Pim Cuijpers is professor emeritus of clinical psychology and scientific director of Metapsy. He has been involved in more than 1,100 scientific studies, mostly on psychological treatments of mental health problems. This is one of a series of evidence summaries in which Prof. Cuijpers tries to answer questions from patients and clinicians, based on what is known in science about treatments. The knowledge is mostly drawn from collective work of the Metapsy collaboration of at least 15 years. Do you have other questions you would like Prof. Cuijpers to discuss? Feel free to contact us.
