Why One-Third of Depression Patients Do Not Respond to Standard Antidepressants
If you are reading this, you have probably tried at least one antidepressant. Maybe several. And the experience likely followed a familiar arc: initial hope, a waiting period of four to six weeks, some partial improvement, a dose adjustment, and eventually the realization that you feel different but not better. Maybe the sadness lifted but left behind a flatness you cannot name. Maybe you gained weight, lost your sex drive, or started sleeping twelve hours and still waking up exhausted.
Here is what most providers do not explain clearly enough: the most commonly prescribed antidepressants, SSRIs and SNRIs, work by increasing the availability of serotonin or norepinephrine in the synaptic cleft. This mechanism helps a meaningful number of patients. But depression is not a single-pathway condition. Current neuroscience identifies multiple systems that contribute to depressive symptoms, including glutamatergic signaling, neuroplasticity and synaptic connectivity in the prefrontal cortex, default mode network hyperactivity, and inflammatory processes that affect neurotransmitter metabolism.
When a patient does not respond to an SSRI, the most common clinical response is to try another SSRI, or switch to an SNRI, or add an adjunct medication. But if the primary driver of your depression is not serotonin availability, cycling through medications that target serotonin is not a strategy. It is a loop.
This is not a fringe position. It is the reason the FDA has cleared and approved treatments that work through entirely different mechanisms. And it is the reason a growing body of research supports a more precise, mechanism-informed approach to treatment-resistant depression.
How TMS and Spravato Target Different Neurobiological Pathways
Transcranial magnetic stimulation (TMS) delivers focused magnetic pulses to the left dorsolateral prefrontal cortex (DLPFC), a brain region consistently associated with mood regulation, executive function, and cognitive flexibility. In patients with depression, the DLPFC is often underactive. TMS works by stimulating neuronal activity in this region, which in turn modulates connectivity with deeper limbic structures involved in emotional processing. A standard TMS protocol involves daily sessions over four to six weeks, and most major insurance plans cover it when the patient has not responded to at least one prior antidepressant trial.
Deep TMS, which uses an H-coil to reach broader and deeper brain regions, is also available at Axis Integrated Mental Health and is FDA-cleared for both major depressive disorder and OCD.
Spravato (esketamine) works through an entirely different mechanism. It is an NMDA receptor antagonist that acts on the glutamate system, the brain’s most abundant excitatory neurotransmitter. By modulating glutamatergic signaling, Spravato promotes rapid synaptogenesis, essentially helping the brain form new synaptic connections. This is a fundamentally different approach from serotonin-based medications, and it explains why patients who have failed multiple SSRIs can experience meaningful improvement with esketamine. Spravato is FDA-approved for treatment-resistant depression and is administered as a nasal spray in-office under clinical supervision. It is covered by most commercial insurance plans when the patient has documented failure of at least two adequate antidepressant trials.
Ketamine-assisted therapy works through a related but distinct mechanism, also targeting NMDA receptors, and can produce rapid mood improvement within hours to days rather than weeks.
The critical point is not that one treatment is universally better than another. It is that these treatments access different neurobiological pathways. A provider who can evaluate which pathway is most likely driving your symptoms, and who is trained across all of these modalities, is in a fundamentally different position than a provider whose toolkit ends at the SSRI formulary.
The Provider Who Can Diagnose at the Level She Treats
Susannah Dowling, PMHNP-BC, brings a combination of clinical capabilities that is difficult to find in a single provider, in Denver or anywhere.
She is trained and certified in the ADOS-2 and ADI-R, the gold-standard instruments for Autism Spectrum Disorder diagnosis. She has administered these assessments at the Kennedy Krieger Institute, one of the nation’s leading centers for neurodevelopmental research. She is a co-author of published research on pharmacotherapy for emotional and behavioral symptoms in pediatric ASD patients (Dialogues in Clinical Neuroscience, 2017). She held a joint faculty appointment at the Johns Hopkins University School of Nursing, where she trained graduate-level PMHNPs.
And she prescribes TMS, Spravato, and ketamine therapy for patients with treatment-resistant depression and anxiety at Axis Integrated Mental Health.
Why does that combination matter? Because psychiatric symptoms do not exist in clean diagnostic categories. A 35-year-old who has cycled through four SSRIs for “treatment-resistant depression” may have an undiagnosed neurodevelopmental condition influencing her symptom profile, her medication metabolism, and her response to therapy. A child presenting with explosive behavior and anxiety may need an ADOS-2 evaluation before anyone writes a prescription. A patient whose depression includes significant cognitive symptoms, brain fog, difficulty concentrating, executive function breakdown, may benefit from TMS targeting the DLPFC specifically because of what a thorough diagnostic evaluation reveals.
Susannah can see the full picture because she has the diagnostic instruments to look for it and the treatment modalities to act on what she finds. That is not a soft differentiator. It is a clinical capability gap that most practices cannot close.
What Happens Between Your Appointments Determines Whether Treatment Works
Here is a question nobody asks on a provider’s website: what happens when you call and nobody picks up?
What happens when your therapist does not know what your psychiatrist prescribed? When your prior authorization takes three weeks and nobody follows up? When you show up for your TMS session and the front desk cannot find your appointment? When you have a medication question at 4pm on a Friday and the only option is an automated voicemail tree?
These are not clinical problems, but they are the reason clinical plans fall apart. And most practices treat them as administrative overhead rather than patient care.
Susannah approaches this differently. Before joining Axis Integrated Mental Health, she served as both a clinical provider and an Operational Excellence Lean Practitioner at Sheppard Pratt, one of the top-ranked psychiatric systems in the country. She holds a Lean Six Sigma Green Belt from the Maryland Patient Safety Center. She did not just earn a certification. She redesigned end-to-end clinical workflows, built data-driven performance tracking for provider productivity, created systematized onboarding infrastructure for new clinicians, and launched a best-practice initiative projected to generate approximately four million dollars in annual revenue.
At Axis, that systems-level expertise translates into tangible patient experience: care coordination that happens proactively between your providers, insurance verification before your first appointment, documentation processes that do not eat into your session time, and a practice infrastructure designed so that the operational side of mental health care never becomes another source of stress in your life.
You should not have to manage the logistics of your own treatment while you are trying to get better. Let our team handle the insurance verification. Schedule a free financial consultation.
Who This Approach Is Built For
You have tried two or more antidepressants without adequate improvement and you are ready to explore whether TMS, Spravato, or ketamine therapy might target the mechanism your previous medications missed. You want to know what your insurance covers before you commit.
You are a parent, a partner, or a family member searching on behalf of someone you love who is struggling, and you need a provider who treats the family as part of the care team rather than an afterthought.
You are navigating a complex or co-occurring diagnosis. Maybe depression plus ADHD, or anxiety with a suspected neurodevelopmental component, or a situation where previous providers disagreed about the diagnosis entirely. You need someone with the diagnostic depth to get it right.
You are a professional running on fumes. You are functional enough that nobody at work has noticed, but you know something is wrong and you need a provider who understands burnout as a clinical condition, not just a buzzword.
You have been dismissed, misdiagnosed, or treated generically by previous providers, and you need someone who will take the time to understand the specifics of your situation before reaching for the prescription pad.
