Genes provide instructions to the brain, which processes our complex thoughts and emotions. The brain does this by producing and breaking down lots of different chemicals, including:
- Other Chemicals
These chemicals do many things:
- Some chemicals send signals.
- Others open and close gates through which other chemicals pass.
- Still others turn on or off the production of proteins. Proteins in turn have countless functions.
Although all of the body’s cells are able to send and receive messages, nerve cells are specially designed for this job.
The chemicals that send messages between these cells are called neurotransmitters. A neurotransmitter’s biological effect depends on how it binds to nerve cells. Neurotransmitters are conserved by nerve cells, and may be reused again at a later time.
Scientists have long thought that problems in mood are connected to the concentration of neurotransmitters and how they bind. Indeed, the drugs used to treat depression have some effect on neurotransmitters or their receptors.
For example, Prozac (generic name, fluoxetine) works by blocking the pump that draws the neurotransmitter serotonin back into the nerve cell that released it. The effect? The concentration of serotonin in the space between cells increases and (in the best case) the person taking the drug becomes less depressed.
It is unknown how the change in serotonin concentration leads to less depression, but there is a connection between the biological change and the mood change. This biological change is popularly described as a “chemical imbalance,” but that term does not fully capture how complicated these processes are.
In addition to serotonin, other neurotransmitters (for example, norepinephrine and dopamine) are likely involved in mood regulation. However, all neurotransmitters have multiple functions. They are involved in everything the brain is in charge of — memory, sleep, appetite, pain, blood pressure, movement and thinking, to name a few.
Whereas each neurotransmitter acts at a very specific spot (the space between nerve cells), hormones circulate through the bloodstream and bring their messages to groups of cells or organs. Some hormones have specific effects, whereas others have a variety of effects.
Hormones are a key to organizing the body’s stress responses and so probably play a role in depression as well. For example, levels of the hormone cortisol ebb and flow depending on your hour-to-hour needs.
Higher cortisol levels allow greater alertness and energy in stressful moments, then levels drop when that need passes. In some people, the feedback mechanism is out of order, and cortisol levels remain too high. This can lead to a variety of problems, including high blood pressure, and may make you more vulnerable to depression.
In addition to neurotransmitters and hormones, numerous other chemicals are involved in the brain’s work. Study is ongoing to evaluate how enzymes, secondary chemical messengers and a variety of small proteins interact with neurotransmitters and hormones to cause changes in mood.