From the Editor

Treatment resistance is a myth!

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For millennia, serious psychiatric brain disorders (aka mental illnesses, melancholia, madness, insanity) were written off as incurable, permanent afflictions. It’s no wonder that they were engulfed with the stigma of hopelessness.

But then came the era of serendipitous discoveries in the mid-20th century, with the felicitous arrival of antipsychotics, antidepressants, and lithium. The dogma of untreatability was shattered, but in its wake, the notion of treatment resistance emerged, and promptly became the bane of psychiatric clinicians and the practice of psychopharmacology.

Many patients with mood and psychotic disorders responded to the medications that were introduced in the 1950s and 1960s, but some either derived partial benefit or did not improve at all. These partial or poor responders were labeled “treatment-resistant,” and caring for them became a major challenge for psychiatric physicians that continues to this day. However, rapid advances in understanding the many etiologies and subtypes of the heterogeneous mood and psychotic disorders are invalidating the notion of treatment resistance, showing it is a fallacy and a misnomer. Let’s examine why.

Treatment-resistant depression (TRD)

Psychiatric clinics and hospitals are clogged with patients who do not respond to ≥2 evidence-based antidepressants and carry the disparaging label of “TRD.” But a patient manifesting what appears to be major depressive disorder (MDD) may actually have one of several types of depression that are unlikely to respond to an antidepressant, including:

  • iatrogenic depression due to a prescription medication
  • depression secondary to recreational drug use
  • depressive symptoms secondary to a general medical condition
  • bipolar depression.

Thus, a significant proportion of patients diagnosed with MDD are labeled TRD because they do not respond to standard antidepressants, when in fact they have been misdiagnosed and need a different treatment.

Even when the diagnosis of MDD is accurate, psychiatric neuroscience advances have informed us that MDD is a heterogeneous syndrome with multiple “biotypes” that share a similar phenotype.1,2 In the past, TRD has been defined as a failure to respond to ≥2 adequate trials (8 to 12 weeks at a maximum tolerated dose) of antidepressants from different classes (such as tricyclic or heterocyclic antidepressants, selective serotonin reuptake inhibitors, or serotonin-norepinephrine reuptake inhibitors). For decades, patients with TRD have been referred to electroconvulsive therapy (ECT), and have experienced an excellent response rate. So TRD is in fact an artificial concept and term, applied to a subtype of MDD that does not respond to standard antidepressants, but often responds very well to neurostimulation (ECT and transcranial magnetic stimulation [TMS]).

When an antidepressant is approved by the FDA based on “successful” placebo-controlled double-blind trials, there is always a subset of patients who do not respond. However, the success of a controlled clinical trial is based on a decline in overall mean depression rating scale score in the antidepressant group compared with the placebo group. Not a single antidepressant has ever exerted full efficacy in 100% of patients who received it in an FDA trial because the sample is always a heterogeneous mix of patients with various depression biotypes who meet the DSM clinical diagnosis of MDD. Most often, only approximately 50% do, which is enough to be statistically significantly better than the roughly 30% response rate in the placebo group. It is impossible for a heterogeneous syndrome comprised of biologically different “diseases” to respond to any single medication! Patients who do not respond to an antidepressant medication that works in other patients represent a different subtype of depression that is not TRD. Biotypes of the depression syndrome have different neurochemical underpinnings and may respond to different mechanisms of therapeutic action, yet to be discovered.

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