What is treatment-resistant schizophrenia?

Schizophrenia is a serious mental health condition involving symptoms in three main groups: positive symptoms (hallucinations, delusions, disorganised thinking), negative symptoms (reduced motivation, social withdrawal, reduced emotional expression), and cognitive symptoms (problems with attention, memory, executive function). For most people with schizophrenia, antipsychotic medication, combined with psychosocial support and (where helpful) psychotherapy, produces substantial improvement.

For a meaningful minority (roughly 20 to 30 percent), schizophrenia does not respond adequately to standard antipsychotic medication. This is treatment-resistant schizophrenia (TRS), defined as failure to respond adequately to at least two adequate trials of different antipsychotic medicines. TRS substantially affects quality of life, functioning, and long-term outcomes, and addressing it well is one of the most important things modern mental health care can do.

Why clozapine matters. Clozapine is an older medicine that was developed before most of the modern atypical antipsychotics. It is the most-evidenced specific therapy for TRS, with substantial evidence supporting its effectiveness in patients who have not responded to other antipsychotics. It is also the only antipsychotic with strong evidence for reducing suicide risk in schizophrenia.

Despite this evidence, clozapine remains underutilised. The reasons include the requirement for regular blood monitoring (because of a small risk of a blood disorder called agranulocytosis), metabolic monitoring (because of effects on weight, lipids, and blood sugar), and the legacy of provider unfamiliarity. Modern integrated clozapine pathways with structured monitoring infrastructure are formalising in major health systems, with the goal of making clozapine more accessible to patients who would benefit.

The therapy approach to TRS.

Clozapine: the foundation. Adequate trial requires sufficient dose and duration, with structured monitoring. Many patients who are designated TRS would respond to adequate clozapine therapy; making sure clozapine is offered when appropriate is the most important quality-of-care question in TRS.

Augmentation for partial clozapine response: in patients who improve on clozapine but retain significant symptoms, options include addition of another antipsychotic (with attention to side effect burden), addition of a mood stabiliser, or ECT augmentation.

Long-acting injectable antipsychotics: for patients with adherence challenges, long-acting forms can substantially improve outcomes by ensuring consistent medication exposure.

Electroconvulsive therapy: an option for selected patients with severe symptoms that have not responded to clozapine optimisation.

Non-pharmacological interventions: cognitive remediation programs, social skills training, supported employment, family-based interventions, peer support, and structured wraparound care all contribute to outcomes. These are often as important as medication choice for long-term functioning.

The emerging direction. KarXT (xanomeline-trospium) is a new mechanism class for schizophrenia (working through muscarinic receptors rather than dopamine receptors directly), approved for schizophrenia broadly in September 2024 and being explored in TRS settings via post-approval research. GlyT1 inhibitor programs (working through glycine signalling) and novel GABA-modulator programs are in late-stage trials. Whether any of these provides meaningful benefit beyond clozapine is being studied.

What to expect. TRS is a serious and difficult condition, but with appropriate care (especially with adequate clozapine therapy when indicated), most patients can achieve meaningful improvement in symptoms and functioning. Care at a specialty clinic with TRS expertise, integrated psychosocial interventions, and comprehensive wraparound care is the standard. The most important things are structured access to clozapine when appropriate, integration of medication with psychosocial supports, and persistent advocacy for the comprehensive care that this condition deserves.