How Does Depression Affect the Brain?

If you have symptoms of depression, it's natural to wonder what's going on in your body. The good news is that researchers have now answered two crucial questions: how does depression affect the brain, and what chemical imbalance causes depression? These discoveries can help you on your journey toward recovery.

Brain cells talk to one another through chemical messengers (also called neurotransmitters) that are released from one cell and passed to the next. Depression is not caused by an imbalance in a single chemical and it's not simply a matter of one chemical being too high or too low. Instead, when someone has depression, we see changes in the normal function and effect of neurotransmitters.

Now, how do these chemical changes cause depression? Take a moment and imagine you're at the airport waiting for a flight connection. Picture the busy, bustling scene around you—hundreds of people all taking different journeys through the same interconnected system. Your brain is like the nation's airport network system. If there are major delays at an airport hub , these have larger effects throughout the rest of the airport network. That is just how it is for depression. Neurotransmitters interact with the brain's "flight paths," or nerve connections, and if one isn't operating properly, it may cause issues elsewhere.

The brain's physical structures (all those airport buildings) are also crucial. Some people who experience depression have subtle differences in these structures. We do not yet know why these variations occur—whether being depressed possibly causes these structural changes, or if the brain changes themselves cause depression.

It's important to remember that depression is not only about what happens within your brain; your life outside of it matters, too. Depression goes beyond those flight paths and those airport buildings. Several factors can interact with one another to trigger depression, including one's genetic blueprint and stress levels, as well as some medications. General health plays a role, too. For example, chronic pain can trigger or increase the chance of depression.

The system mainly implicated in depression is the limbic system. This is a set of structures concerned with emotions and memory, all underpinned by the hard work of those neurotransmitters.

Here are some of the major structures that appear to show subtle differences in some people with depression:

• The hippocampus is associated with emotions and memory storage. It's susceptible to the effects of stress hormones, such as cortisol. If you experience long-term high levels of stress, that can increase your cortisol levels, which, in turn, affects the growth of nerve cells within the hippocampus. This may explain why many people with depression report memory and concentration difficulties. Numerous studies have shown that changes in the hippocampus can be reversed with depression treatment.
• The hippocampus influences the functioning of the prefrontal cortex , the region toward the front of your brain. This region helps with decision-making, attention, and social behavior. Brain scans show minor and reversible changes in the prefrontal cortex. This could account for troubles with attention and decision-making seen in some with depression.
• The amygdala is a structure deep within the brain that is associated with certain emotions, such as sorrow, fear, anger, and pleasure. Activity in the amygdala is higher when someone experiences depression. Like the hippocampus, it is sensitive to consistently high levels of cortisol. This increased activity in the amygdala could influence sleep patterns; up to 90 percent of people with depression report insomnia.
  

There are two promising and constructive messages to take from this evolving science.

Firstly, these brain changes are reversible—they can be remedied. Some depression treatments might even trigger the growth of new nerve cells and strengthen novel connections between cells.

Secondly, our understanding of the brain's biology has helped researchers design targeted and effective depression treatments. This knowledge could deliver treatments to you with a dedicated approach that suits you best.

Knowing which brain connections are affected has helped to unravel some of the mysteries of depression. Now, it is driving game-changing treatment options.

Transcranial magnetic stimulation (TMS) is a non-invasive and non-drug form of brain stimulation that goes far beyond correcting one chemical imbalance or one disrupted network connection. Instead, it addresses the complex brain changes of depression—those neurotransmitter and connectivity issues discussed earlier.

TMS applies highly focused magnetic pulses to brain regions that are crucial in the regulation of mood. Those focused magnetic pulses result in activation of the nerves in that area of the brain, which when given over time, can correct imbalances in function. Research supports its ability to form new connections between nerve cells affected by depression, including those within the hippocampus . It can help to relieve some, or even all, depression symptoms in many patients.

Understanding the science of depression has taken years, and there is still much more to learn. But in our quest to answer those vital questions—how does depression affect the brain, and what chemical imbalance causes depression—we have uncovered tailored treatments that acknowledge everyone's unique experiences.

This personalized knowledge can empower you to finally navigate your way toward recovery. Just like those airport hubs with their temporary flight delays, there are ways to get back on track once again.