How antidepressants work, according to a psychiatrist

• Depression medications affectthe concentration of certain neurochemicals in the brain, and/or their receptor sites.
• The word "antidepressant" actually refers to several different kinds of medication.
• There remains quite a bit to be understood about how and why these drugs reduce symptoms of depression, including why some drugs work for some people and not others. But there is sufficient evidence to support that they do in fact help many people.

Prozac, Lexapro, Zoloft, Cymbalta – whatever the drug, there's a lot of stigma and misconceptions around antidepressants. The first thing to understand about antidepressant medication is that it doesn't exactly just make a person happier – it's more complicated than mood alteration.

Dr. Philip Muskin, psychiatrist at New York-Presbyterian/Columbia University Irving Medical Center, spoke to INSIDER about how these medications actually affect people who live with depression and related mental illnesses.

SEE ALSO: The biggest myths about depression

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All antidepressants work by affecting the concentration and function of neurotransmitters.

The nervous system is unique in that its cells, called neurons, don't touch. Neurons communicate instead using neurotransmitters.

What antidepressants do, Muskin said, is "alter the concentrations of these various chemicals that are called neurotransmitters, in the space between the two neurons, called the synapse."

The specific neurotransmitters involved in depression and its treatment are serotonin, norepinephrine, and to a slightly lesser extent, dopamine. These neurotransmitters all serve various functions that involve mood, like regulating anxiety and depression, allowing us to feel euphoric.

They also serve various other functions that are not directly related to mood, like stimulating nausea and maintaining bone health in the case of serotonin, for example.

"[Antidepressants] also have an impact on the receptor sites, which is just a fancy way of saying sort of a biological lock, where the neurotransmitter is the key," Muskin said. "Some have a very strong affinity for these receptor sites, and some have a weak affinity."

The word "antidepressant” refers to several different kinds of drugs.

"Antidepressant" is a very broad term that can refer to any type of drug used to treat depression, no matter its actual neurological effect.

Over the last century, various kinds of medicines, usually developed for other purposes initially, were found to help people suffering from depression.

If we say someone is taking an antidepressant medication, that could mean they're taking any number of different kinds of medications: SSRIs (selective serotonin reuptake inhibitors), SNRIs (selective norepinephrine reuptake inhibitors), MAOIs (Monoamine oxidase inhibitors), lithium, or even stimulants.

The exact effect of an antidepressant depends on which type of drug we're talking about. SSRIs, for example, make more serotonin available in your brain by preventing the cells that put it out from reabsorbing it.

Different drugs work for different people, and we’re not really sure why.

Though scientists and doctors know enough to understand the specific chemical effects of these drugs, it's not entirely clear why making more or less of a certain neurochemical available helps alleviate depression for some people – and why it doesn't help others.

"All the drugs are subtly different, and that doesn't really account for whom they work. No drug works for everybody. But every drug works for somebody. And we don't understand why that is," says Muskin.

"We know exactly what [the drugs] do, which is to say their chemical effect. Can we say reliably, 'This is why a person who is depressed gets better'? No."

This is why antidepressant medication tends to be trial-and-error. It's not uncommon for someone with depression to try a medication and feel no effect, or to experience unbearable side effects, and then switch to a different drug in hopes of a better fit. It can take time for a patient and their psychiatrist to figure out what works.

Antidepressants are often also used to treat other conditions.

Not everyone taking antidepressants actually has depression – some of the same medications are used to treat other diagnoses altogether. Fluoxetine (the generic name for Prozac), for example, is also used to treat panic attacks, bulimia, and Obsessive-Compulsive Disorder.

There are even some (admittedly exceptional) conditions where stimulants like Ritalin, most commonly used as an ADHD treatment, are prescribed to help depression sufferers alleviate their symptoms.

There is a lot of uncertainty around how and why certain drugs help alleviate depression, but the fact remains that they do work.

"For some people on antidepressants, we see new cell growth in the hippocampus," which is thought to be the emotion and memory center of the brain, Muskin said. "We don't know what that means, but we think it's a good thing."

While there is still plenty of research to be done, Muskin emphasized that there is enough certainty to know that psychiatric drugs do work – often to great effect.

"We know that they typically take a few weeks to take effect," he said, but when a patient finds the right one, it can make a world of a difference.

"These are great drugs. They've helped many, many people."

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