Gray matters: The role of sentience in depression

Though it is often debated, many professionals suggest the earliest age at which clinical depression can be diagnosed is 3 years old.

While depression may look very different in adult cases, many believe that certain risk factors manifest through a child’s social development.

According to the Brain & Behavior Research Foundation, these signs include a child being in a negative mood for more than two hours a day and being easily tipped into those negative moods.

Of course, the thing that most likely distinguishes early-onset depression in children from adults is a level of awareness and cognitive development that children do not yet have.

Whether that awareness makes the disorder easier or harder to deal with is unclear. On the one hand, awareness allows one to keenly compare themselves to others and potentially hate themselves for the state they are in.

On the other hand, awareness may be the only path to betterment, encouraging one to acknowledge their behaviors and choose to seek help. 

To perhaps a larger extent, this is simply a matter of definition. Of course, the most fundamental symptoms of depression, which professionals have decided are anhedonia — a lack of interest in “human” pleasures like eating, sex and accomplishing goals — and a prolonged negative emotional state, occur in both children and adults.

But while they are unquantifiable, the differences between those experiences in an undeveloped and unaware mind versus a developed and aware one are probably vast. 

This makes studying depression very difficult: it’s a condition that will appear differently in just about every single person.

Depression, as we currently understand it, is simply a cluster of symptoms. And typically we expect that wherever there are symptoms, there is disease. 

Research surrounding mood disorders like depression is becoming increasingly biological, with the goal of discovering whether there is something in the brains of depressed people that can be “corrected” to alleviate symptoms.

Many researchers are looking for biomarkers for depression. This involves finding a deficit in depressed brains as compared to non-depressed brains, and trying to establish it as causal. In other words, identifying a part or a feature of the brain that is causing depression-like symptoms, so that we can understand what to target in terms of treatment.

One such biomarker that has some potential is anterior insular cortex volume, which is shown to be reduced in both current and remitted major depressive disorder patients.

Several other correlates have been found in different areas of the brain, but what remains unclear about all of them is the specific role they play in facilitating the symptoms of depression that many of us are familiar with.

Many of these correlates have been found using brain imaging on humans, particularly MRI, which only shows structure.

The next best thing to study is animals. And while I want to refrain from comparing human children to animals, they have something very important in common — a lack of awareness present in adults.

Researchers have come up with ingenious methods by which they try to make animals depressed. They sometimes seem a bit cruel, but they are still unable to address what may be the most fundamental aspect of adult depression — human consciousness.

One method is the chronic unpredictable stress paradigm, which involves subjecting a mouse to a shock or an otherwise adverse event at random times until it gets tired of being worried. Another is allowing a mouse to be bullied until it acts depressed.

While it is important to acknowledge that these paradigms have given us many insights as to how certain emotional circuits may work, it is also important to recognize that studying depression in animals may be like studying flying in humans by taping wings to their backs. Just because a depressed animal may act like a depressed human, there is no indication that the internal processes facilitating those behaviors are comparable at all.

You can make a mouse act in ways analogous to a depressed person, but it would be tough to make that mouse feel like a burden to every other mouse in its life, feel guilty about its sadness and hopefully eventually understand what it can do to make its life better.

Our current closest approximation to the real thing, in animal models, is very likely not good enough for a full understanding of depression in humans.

The most probable source of optimism lies in the potential of future technology being able to better visualize a human brain while it is active. I’ve talked about some of these future possibilities in another piece.