What does the levels problem refer to? 

The levels problem in psychopathology refers to the fact that psychopathological disorders are investigated in different ways (or at different levels). Most frequently, these include the psychological level and the biological level. The boundary between these two levels is blurry, and it may be difficult at times to differentiate between them. For example, autism is not only a psychological disorder but also a biological one, so from what level should it be analyzed? As will be explained in the next section, there are also multiple different ways of categorizing levels. Since these categorizations have much overlap, levels should not be taken too literally, and should instead be used for heuristic purposes. The level problem makes it more difficult for researchers and clinicians to decide the best framework for advancing psychopathology research.

What are three ways of thinking about levels? 

Three common ways of conceptualizing different levels are the following: part-whole related levels, levels based on the scale of what is being measured, and levels based on the time range of what is being measured. Although these are not the only ways to think about levels, they are the most relevant in terms of psychopathology. To begin, part-whole levels refer to hierarchies, for example, within an organism. An organism can be broken down into tissues, cells, cell parts, molecules, and eventually atoms. The whole of an organism is at a higher level than that of its parts — thus, it is a hierarchical structure. This hierarchical system of levels, however, can vary even within the same organism, as what is considered a higher or lower level is determined by what is being measured. Additionally, the concept of part-whole levels is not always clear-cut. Ideally, there would be no overlap between levels in the hierarchy and no components that would fall between levels, but this is seldom the case in practice. There is also no agreed-upon way to decide with consistency which component belongs to which level in the part-whole system. 

Levels can also be thought of in terms of scales. Essentially, this means that the size of the thing being studied is what determines its level. The example of analyzing the activity of neurons is given in the article. In functional neuroimaging, each data point consists of millions of neurons, whereas cellular neuroscience analyzes neurons individually. In this case, the scale of functional imaging is much broader. Finally, there is the temporal scale, in which the length of the process being studied determined its level. For example, the interactions between brain areas take much longer than the interactions between neurotransmitters and receptors. Importantly, the temporal scale can be applied quite easily to the concept of psychopathology, because the time that it takes for symptoms and mental states to appear, progress, and fade can be measured and compared to the time it takes for neurobiological states to change.

What are explanatory reductionism and explanatory pluralism? 

People that take an extreme explanatory reductionist view believe that the neurobiological mechanisms of the brain make explanations at the psychological level useless. They think that the only reason psychological-level explanations are accepted as explanations at all is because we do not know the neurobiology behind those explanations yet. Those who subscribe to a more lenient version of explanatory reductionism believe that psychological explanations are real, but will never be as important or powerful as explanations on the neurobiological level. All explanatory reductionists think that biological explanations, which are on a lower level, are more useful than psychological explanations, which are on a higher level. This is partially due to explanatory reductionists’ reasoning that all behavior is merely an outward expression of biological activity, which in “mind-body debate” terms is a monism view. In past scientific research, it has often been very helpful to study the lowest biological levels. DNA, for instance, was discovered this way. However, it is not always sensible to ignore higher levels. In physics, for example, investigating only very low levels like molecules is not sufficient for actually explaining and predicting physical laws and behavior on a higher level. 

In the context of psychopathology, explanatory pluralism is more useful than explanatory reductionism. Explanatory pluralism advocates not just for exploring higher levels, but for investigating multiple levels (both higher and lower) in the context of one concept. Explanatory pluralism is most useful when the information received from each level is integrated into a more comprehensive system. Integrating all this information may mean that professionals from many fields have to compile and align concepts related to a specific psychological problem.

Why is examining psychopathology from a higher-level useful?

The field of clinical psychology relies on higher-level explanations of psychopathologies because it is exceedingly difficult to discover genes or other biological anomalies that wholly or substantially explain a specific psychiatric disorder. It is very unlikely that something as low level as a strand of DNA can ever explain something as high level and abstract as a mood disorder, for instance. On the other hand, researchers have made much progress in understanding the causes and subtypes of obsessive-compulsive disorder through analyzing the disorder's typical cognitive processes. Considering this, it would be prudent for psychopathological research to be done at multiple levels which differ in time, scale, and part-whole hierarchies.