Do Antidepressants Work If Depression Is Not a Chemical Imbalance?

Antidepressants Can Work Even Though the Old Explanation Was Too Simple

Do antidepressants work if depression is not caused by a chemical imbalance? Yes. Those two ideas are not contradictory, but for years patients were often given an explanation that made them sound contradictory. Many people were told that depression happened because the brain did not have enough serotonin and that an antidepressant corrected the problem by replacing or restoring that missing chemical. It was easy to understand, but the biology of depression and antidepressant treatment is much more complicated.

A major systematic review examining the serotonin theory found that the available evidence does not support the simple claim that depression is caused by abnormally low serotonin levels or activity. Read the serotonin theory umbrella review on PubMed. That does not mean serotonin is irrelevant to the brain, and it certainly does not mean medications that affect serotonin are useless. It means we should stop confusing a medication's mechanism with proof of the disease's original cause.

A simple analogy helps. Acetaminophen can reduce a headache, but headaches are not caused by an acetaminophen deficiency. Blood-pressure medication can lower blood pressure without proving that hypertension was caused by a deficiency of that medication. In the same way, an antidepressant can improve depression without depression having been created by a shortage of the chemical that medication influences.

The History of Antidepressants Helps Explain the Confusion

The history of antidepressant medication is surprisingly useful because the first modern antidepressants were not invented after scientists discovered the cause of depression. Instead, their antidepressant effects were discovered partly by accident.

In the 1950s, a medication called iproniazid was being used in the treatment of tuberculosis. Clinicians noticed unexpected improvements in mood among some of the patients receiving it. That observation helped lead to iproniazid becoming one of the first modern antidepressants. Historical reviews of psychopharmacology confirm that iproniazid began as an anti-tuberculosis medication before its antidepressant properties were recognized. Read the history of antidepressant discovery on PubMed

That history matters because physicians knew the medication could improve depression before they fully understood why it worked. Later researchers discovered that iproniazid altered monoamine signaling, and other antidepressants were subsequently developed that affected serotonin, norepinephrine, dopamine, or combinations of those neurotransmitter systems. From there, it was tempting to work backward and conclude that because medications changing those systems improved depression, depression must have been caused by abnormalities in those chemicals. That conclusion was understandable, but it was too simple.

Changing Serotonin Does Not Prove Low Serotonin Caused the Depression

Selective serotonin reuptake inhibitors, or SSRIs, do exactly what their name describes: they inhibit the transporter that normally moves serotonin back into the neuron after it has been released. That changes how serotonin signaling occurs between neurons. But knowing what the medication does does not tell us that the patient's original problem was “not enough serotonin.”

This distinction becomes even more obvious when we consider timing. SSRIs begin affecting serotonin transport relatively quickly, yet meaningful clinical improvement often develops over a much longer period and appears to depend on downstream changes throughout neural networks. Researchers have therefore spent decades studying the adaptations that occur after the initial neurotransmitter change rather than assuming that the first chemical effect explains the entire antidepressant response. Review antidepressant action and neuroplasticity on PubMed

This is why I prefer explaining antidepressants as medications that change brain signaling in ways that can help struggling neural systems function more effectively. That explanation is not as catchy as “you have low serotonin,” but it is much closer to reality.

Antidepressants Affect Much More Than One Neurotransmitter Level

The brain is not a bucket of serotonin where depression appears when the fluid level gets too low. Brain cells communicate through complicated networks involving serotonin, norepinephrine, dopamine, glutamate, GABA, hormones, inflammatory signals, neurotrophic factors, electrical activity, learned patterns, and many other processes that continue interacting with each other.

Antidepressants begin by affecting particular neurotransmitter systems, but the effects do not stop at the synapse where the medication first acts. Research has linked successful antidepressant treatment with changes in neuroplasticity, meaning the brain's ability to strengthen connections, reorganize networks, and adapt. Studies have also found relationships between antidepressant treatment and brain-derived neurotrophic factor, or BDNF, which participates in neuronal plasticity and maintenance. Review antidepressants, BDNF, and neuroplasticity on PubMed.

I would not simplify that into another slogan and say, “Depression is a BDNF deficiency.” That would simply repeat the same mistake with a different molecule. The important point is that antidepressant action appears to involve far more than raising the concentration of one chemical.

The Evidence Still Shows That Antidepressants Can Work

Once people learn that the serotonin-deficiency explanation is too simple, some jump to the opposite conclusion and say, “Then antidepressants don't work.” That conclusion is also wrong.

One of the largest analyses of modern antidepressants examined 522 randomized trials involving more than 116,000 adults with major depressive disorder. All 21 antidepressants included in the analysis were more effective than placebo during acute treatment, although effectiveness and tolerability differed among medications and among patients. Read the large antidepressant network meta-analysis on PubMed

That is why the scientifically defensible position is not “antidepressants fix a serotonin imbalance,” and it is not “antidepressants are fake.” The better conclusion is that antidepressants have demonstrated clinical efficacy, but the reason they work is more complicated than the old chemical-imbalance story suggested. That nuance matters because patients deserve both sides of the truth.

Antidepressant Response Does Not Tell Us What Originally Caused the Depression

Another common mistake is assuming that if medication works, the depression must have been biological, while if therapy works, the depression must have been psychological. Human beings do not separate that cleanly.

Someone may become depressed after years of unresolved trauma, an unhealthy relationship, severe occupational stress, chronic avoidance, loneliness, or loss of purpose. An antidepressant may still improve that person's sleep, emotional regulation, anxiety tolerance, concentration, and ability to function. That improved functioning may then give them enough stability to participate more effectively in therapy and change the circumstances contributing to the depression.

The medication did something useful. That does not mean the original marriage problem, trauma, social isolation, or professional failure was caused by serotonin.

The reverse is also true. Someone with substantial biological depression may benefit from therapy because therapy changes behavior, relationships, cognition, emotional regulation, stress response, and ultimately brain function as well. “Biological” and “psychological” are not competing worlds when psychological experiences occur inside a biological brain.

I Sometimes Describe Antidepressants as Helping the Brain Get Stronger

In Conquering PTSD, I use a deliberately simplified analogy and say that if I could rename antidepressants for patients, I might call them something closer to “frontal lobe strengtheners” or “neuron strengtheners.” That is not a formal pharmacological name, and I am not suggesting that an SSRI simply repairs one isolated portion of the brain. It is a patient-friendly way of communicating that the usefulness of these medications goes beyond correcting a supposedly low serotonin number.

Modern neuroplasticity research fits reasonably well with that broader concept. Antidepressant treatment has been associated with changes in neuronal plasticity, BDNF signaling, neurogenesis in experimental models, and the ability of neural networks to adapt. Read a review of antidepressants and neuroplasticity on PubMed

The metaphor becomes especially useful clinically because many patients tell me, “The medication did not make my problems disappear, but suddenly I could handle them better.” They may notice that it takes more stress before they become overwhelmed, that they recover faster after something difficult, that anxiety is less paralyzing, or that they finally have enough energy and emotional stability to begin solving problems that previously felt impossible. That is often exactly what we need the medication to accomplish.

Antidepressants Can Help With Anxiety Even Though They Are Called Antidepressants

The name “antidepressant” creates another misunderstanding because these medications are frequently useful for conditions that are not primarily depression. SSRIs and SNRIs are commonly used in anxiety disorders, panic disorder, obsessive-compulsive disorder, PTSD, and other conditions.

That makes more sense once we stop treating the medication name as a description of the disease mechanism. A medication called an antidepressant is not a substance that exclusively attacks “depression chemicals.” It alters brain signaling in systems that participate in multiple emotional and cognitive functions.

This is also why in Conquering PTSD I discuss antidepressant medication with a patient whose larger problem involved PTSD, anxiety, mood regulation, concentration, sleep, and emotional functioning rather than depression alone. The clinical question was not whether his diagnosis had the word “depression” in it. The question was whether medication could help the parts of his brain that were struggling function better enough for him to do the rest of the work.

Medication Can Create Enough Stability for Therapy to Work Better

There are patients who intellectually understand what needs to change but are too depressed or anxious to implement it. They cannot sleep. Their thoughts are slowed or chaotic. Minor stress becomes overwhelming. They cannot concentrate during therapy. Their energy is so poor that even basic responsibilities feel impossible.

In those situations, telling the patient to simply work harder is not useful. Medication may help restore enough functioning that the person can finally engage with treatment. They can remain in a difficult therapy conversation longer. They can think more clearly before reacting. They can sleep enough to have emotional reserve the next day. They can begin taking the behavioral steps necessary to rebuild their life.

That is why I do not see medication and therapy as rivals. Our active Medication Management program at Dynamic Psychiatry & Wellness is built around structured evaluation and ongoing adjustment rather than simply prescribing a pill and hoping it works. When appropriate, medication becomes one tool inside a broader treatment plan.

Medication Does Not Have to Be the Entire Treatment Plan

The fact that antidepressants work does not mean medication should automatically become the only treatment. If someone is depressed because several important areas of life have collapsed, medication may help their brain function better while those areas still need to be rebuilt. If trauma is driving symptoms, trauma treatment may remain necessary. If thyroid disease, hormonal changes, sleep apnea, medication side effects, or another medical problem is contributing, those issues still need attention.

This is one reason our Depression Treatment program includes medication, therapy, and advanced options rather than assuming every patient needs the same pathway. The purpose of medication is not to give us permission to stop asking why the patient became depressed.

Sometimes medication alone produces an excellent recovery, particularly when the episode is primarily responsive to pharmacological treatment. Other times the medication produces partial improvement and reveals what still needs attention. Both outcomes are useful information.

A Partial Response Does Not Mean the Medication Failed

Patients sometimes evaluate medication in all-or-nothing terms. They start an antidepressant, improve 30 or 40 percent, and conclude that it “didn't work” because they still have symptoms. I see that differently.

A partial response may be extremely valuable. If a patient goes from being unable to work to working again, from sleeping two hours to six hours, or from being overwhelmed by every minor stressor to tolerating enough discomfort to participate in therapy, the medication has done something important even if the patient is not yet fully well.

The next question becomes why the remaining symptoms are still present. Perhaps the medication strategy needs further adjustment. Perhaps therapy now has work to do. Perhaps sleep, hormones, trauma, relationships, medical contributors, or avoidance are still driving part of the depression. Treatment should use the response as information rather than forcing a binary judgment of success versus failure.

The Right Antidepressant Can Differ From One Patient to Another

Antidepressants are also not one uniform category. SSRIs, SNRIs, bupropion, mirtazapine, tricyclic antidepressants, monoamine oxidase inhibitors, and other medications affect brain signaling differently. Even medications in the same class can feel very different to individual patients.

One person may experience excellent improvement with the first medication they try. Another may have side effects. Someone else may get partial benefit. A fourth patient may require a different class entirely. This variability is one reason psychiatric prescribing should not become random trial-and-error, but it is also why no laboratory test currently tells us with perfect accuracy which antidepressant will work best for every individual.

At Dynamic Psychiatry & Wellness, the goal of medication management is therefore to use diagnosis, symptoms, prior response, side-effect history, physiology, comorbid conditions, and ongoing response to make treatment progressively more precise rather than changing medications without understanding what happened.

Side Effects Still Matter

Defending antidepressants from an inaccurate chemical-imbalance debate does not mean pretending the medications are harmless. They can cause side effects, and those effects differ between medications and patients. Sexual dysfunction, gastrointestinal symptoms, sleep changes, fatigue, activation, emotional blunting, appetite or weight changes, and other effects may influence whether a medication is worth continuing.

The right question is not, “Does this medication have any risk?” Virtually every effective medical treatment has potential risk. The useful question is whether the expected benefit outweighs those risks for this patient and whether there is another option that offers a better balance.

This is also why patients should not abruptly discontinue antidepressant medications because they have read that the chemical-imbalance theory is outdated. Stopping some antidepressants suddenly can produce significant discontinuation symptoms and can also increase the risk of recurrence of the underlying illness. Medication changes should be planned with the prescribing clinician.

If One Antidepressant Does Not Work, the Answer Is Not Always Another Antidepressant

There is another mistake on the opposite end of the spectrum. Once treatment begins with medication, clinicians and patients can fall into a pattern where every incomplete response automatically leads to another medication trial without stepping back to reconsider the larger picture.

After several disappointing treatments, it becomes increasingly important to ask whether the diagnosis is accurate, whether bipolar disorder, ADHD, trauma, sleep disturbance, hormones, thyroid disease, substance use, medical illness, relationship problems, or another factor has been missed. Sometimes the depression truly is treatment-resistant and requires a different biological intervention. Other times the person has been receiving treatment for the wrong problem.

That is why our Treatment-Resistant Depression program begins with further evaluation rather than simply assuming that the next pill will solve the problem.

TMS and Ketamine Further Prove That Depression Is Not One Simple Chemical Problem

Modern depression treatment itself demonstrates how incomplete the old serotonin story was. Transcranial Magnetic Stimulation does not treat depression by putting more serotonin into the bloodstream. TMS uses targeted magnetic stimulation to influence brain networks involved in mood and cognitive regulation. Learn about TMS at Dynamic Psychiatry & Wellness

Ketamine works through another pathway, involving glutamatergic signaling rather than functioning like a traditional SSRI. It can help selected patients whose symptoms have not responded adequately to standard treatment. Learn about IV Ketamine-Assisted Therapy

The fact that very different treatments can improve depression should make us cautious about insisting there must be one universal biochemical defect underneath every case. Depression is more complicated than that, and the treatment options are becoming more sophisticated because our understanding is becoming more sophisticated.

Antidepressants Work Best When We Stop Asking Them to Prove Too Much

I think much of the argument around antidepressants comes from asking the medication to prove something it was never capable of proving. If an antidepressant works, that does not prove depression was caused by low serotonin. If it does not work, that does not prove the depression is not biological. If therapy works, that does not prove the illness was “all psychological.” If TMS works, that does not prove medication was inappropriate.

Each treatment provides information about what helps the patient recover.

The medication's job is not to explain the entire history of the depression. Its job is to improve the patient's functioning enough to justify the benefits, risks, and cost of taking it.

That is a much more useful standard.

The Better Question Is Not “Do Antidepressants Work?”

We already have strong evidence that antidepressants can work. The more useful questions are whether this antidepressant is likely to help this patient, whether the dose and treatment strategy are appropriate, whether side effects are acceptable, whether the patient is actually improving, and what other contributors still need treatment.

For some patients, antidepressants are transformative. For others, they provide partial support. Some patients do poorly with them and require another strategy. None of those experiences changes the fact that the old chemical-imbalance explanation was overly simplistic.

This is why I am comfortable holding two ideas at the same time:

Depression is not simply caused by low serotonin. Antidepressants can still be very effective.

Those statements only appear contradictory if we assume a medication must replace a missing substance in order to work.

Medication Is a Tool, Not a Theory of the Patient

At Dynamic Psychiatry & Wellness, I do not want patients to leave medication management thinking that the medication explains who they are or why every struggle developed. Medication is one treatment tool. It may strengthen functioning, reduce depressive symptoms, make anxiety more manageable, restore sleep, improve motivation, and give someone enough stability to begin changing the things in life that also need attention.

But we still want to understand the cause.

That may include biology, genetics, stress, trauma, relationships, avoidance, social isolation, sleep, thyroid function, hormones, medical illness, purpose, accomplishment, or several of those factors interacting at the same time.

The more accurately we understand the patient, the more intelligently we can decide where antidepressants fit. The chemical-imbalance story may have been too simple. The answer is not to throw away antidepressants. The answer is to use them with a better understanding of what they can—and cannot—do.