The Costs
Against modest efficacy, psychiatric medications carry a side-effect burden that is often underplayed. Sexual dysfunction affects 40–65% of patients on SSRIs and SNRIs (serotonin–norepinephrine reuptake inhibitors) — for some, persisting after discontinuation. Emotional blunting — a flattening of both positive and negative emotions — is reported by 60% of antidepressant users, with similar proportions reporting they “didn’t feel like themselves.” Withdrawal effects affect 56% of patients on discontinuation, with 46% describing those symptoms as severe. For benzodiazepines, 20–45% of long-term users experience significant withdrawal, and physical dependence can develop over months. Antipsychotics carry their own distinct burden: tardive dyskinesia (involuntary, often irreversible, movement disorders) affects approximately 30% of patients on first-generation agents. Nearly 60% of psychiatric outpatient visits in the US involve prescriptions for two or more psychotropic medications, with limited evidence supporting most combinations.
Prescribing has expanded enormously: in England, antidepressant prescriptions more than tripled between 1998 and 2018 (18.4 million to 70.9 million per year). This has been driven not by more people starting treatment but by increasing duration of use — patients staying on antidepressants for years, often indefinitely, despite clinical trial evidence usually only extending to 6–12 weeks. The majority of prescriptions are written by GPs, and the infrastructure for regular medication reviews is inconsistent. Patients may begin usage during a crisis, stabilise, and continue indefinitely because no one revisits the decision.
The Industry’s Retreat
Although psychiatric drugs are more widely used than ever before, the pharmaceutical industry has largely abandoned the search for improved treatments. Over the past fifteen years, the world’s largest drug companies have systematically stopped psychiatric drug development: GlaxoSmithKline closed psychiatric labs (2010), Novartis shuttered its Basel neuroscience facility (2011), AstraZeneca discontinued and then fully exited (2012–2024), Pfizer pulled out entirely, cutting 300 research positions (2018), and Amgen ended its neuroscience programmes (2019). Although psychiatric drugs represent a global market of around $50 billion, this is now largely in generics. The science of novel drug development kept failing, reducing incentives for innovation. The probability of a psychiatric compound progressing from Phase I to regulatory approval is 6.2% — among the lowest of any major therapeutic area. The most dramatic recent illustration came in 2024, when AbbVie’s emraclidine — acquired through an $8.7 billion purchase of Cerevel Therapeutics — failed its Phase II trial. AbbVie took a $3.5 billion impairment charge and lost $40 billion in market capitalisation in a single day.
There are recent exceptions — esketamine (2019) targeting NMDA glutamate receptors for treatment-resistant depression (although ketamine has again been in use since the 1960s — this should be recognised as a newly approved psychiatric application of older pharmacology), and Cobenfy (2024), the first antipsychotic in over fifty years to work through a non-dopamine mechanism — but these remain isolated breakthroughs rather than evidence of a new paradigm.
Signal or Malfunction?
From an evolutionary perspective, the pharmaceutical approach to mental health has a fundamental problem: it has largely assumed that symptoms are expressions of dysfunction, when many can also be evolved functional responses carrying information. The real challenge is to distinguish functional signals from genuine dysfunction — and to target treatment accordingly. At present, both are too often treated as the same problem. When a patient presents with anxiety or low mood, the standard pharmacological response is to treat the symptom. But where those emotional states are evolved functional responses carrying information — anxiety signalling threat, low mood signalling that a life strategy is failing — treating the response without also reading what it is signalling is the equivalent of silencing a smoke alarm without ever checking whether there is a fire.
The analogy with pain is instructive. Pain is an evolved signal, and we have excellent painkillers. Nobody would argue that painkillers are never appropriate — they are among the most valuable tools in medicine. But no competent physician would prescribe painkillers instead of investigating the source of the pain. A patient with a broken leg needs both pain relief and a splint. A patient with appendicitis needs both pain management and surgery. Painkillers that masked a serious injury and allowed the patient to keep walking on a fracture would not be considered good medicine — they would be making the underlying problem worse by suppressing the signal that would otherwise prevent further damage. Psychiatric medication, when used without an understanding of what the symptoms are for, risks doing exactly this: relieving the signal while leaving the cause untouched, and sometimes allowing the cause to worsen. The patient feels better in the short term, but the conditions that triggered the evolved response — perhaps social isolation, a mismatched environment, an exploitative relationship — remain unchanged. In some cases, the medication may actively prevent the adaptive response: a depression that would otherwise have motivated someone to leave an exploitative job or a harmful relationship is suppressed, and the person remains in the situation causing their suffering.
This does not mean that psychiatric medication is never appropriate — just as the existence of pain does not mean we should never use painkillers. For severe depression, psychosis, and acute crises, pharmacological intervention can be life-saving. The evolutionary critique is not anti-medication; it is anti-indiscriminate-medication. The question is not “should we ever use these drugs?” but “do we understand what we are suppressing and confirming suppression is the right response?” At present, for the vast majority of prescriptions, the answer is no. But shifting the perspective on the problems of psychiatry to one informed by evolutionary biology offers two transformative contributions that could change this: better phenotyping, and better outcome measures. Each deserves detailed attention.
Cutting Through the Heterogeneity: Evolutionary Phenotyping
One of the central problems in psychiatric pharmacology is heterogeneity. A patient who presents with low mood, sleep disruption, loss of appetite, and social withdrawal receives a diagnosis of major depressive disorder. But this diagnosis tells the prescriber almost nothing about why this person is depressed — and without knowing why, there is no principled basis for choosing a treatment. The same symptom profile could reflect grief after bereavement, chronic social entrapment, inflammation-driven sickness behaviour, seasonal changes in light exposure, or genuine neurobiological dysfunction. These are categorically different problems with categorically different causes. Yet under the current diagnostic system, they all receive the same label and, in most cases, the same prescription.
Depression, from an evolutionary perspective, is not one disease. It is a generic response — much like pain — in which the organism reduces activity, withdraws from engagement, and conserves resources. Just as pain can signal a broken bone, a burn, a bacterial infection, or a torn muscle, depression can be triggered by fundamentally different circumstances involving different evolved pathways. Rantala and colleagues’ 2018 paper suggested twelve distinct subtypes of depressive episodes based on their proximate triggers and evolutionary functions, including infection-related depression, long-term stress, loneliness, traumatic experience, grief, romantic rejection, hierarchy conflict, postpartum hormonal changes, seasonal variation, chemical exposure, somatic disease, and starvation. Hagen’s critical review of evolutionary theories proposes that some forms of depression may function as social bargaining strategies in cooperative relationships, while others represent social navigation mechanisms that emerge when an individual’s major life strategies are blocked.
The same principle applies to anxiety. Social anxiety and panic disorder may both produce avoidance behaviour, but they involve fundamentally different evolved systems. Social anxiety relates to our evolved sensitivity to social hierarchy and group acceptance: humans are a deeply social species, and being excluded from the group was, for most of our evolutionary history, a death sentence. Social anxiety arises from the system that monitors the risk of exclusion and motivates appeasement, status-seeking, or withdrawal when that risk is high. Panic disorder, by contrast, seems to activate the ancient predator-defence system — the freeze–flight–fight cascade that evolved to respond to immediate physical danger. Generalised anxiety may reflect a threat-detection threshold set too low — the smoke detector principle in overdrive — where the system that evolved to err on the side of caution in genuinely dangerous environments is firing constantly in a modern world that triggers it far more often than the one in which it was calibrated. These are different systems, shaped by different selection pressures, operating through different neural circuits.
The implications for pharmacology are profound. A drug that dampens the predator-defence arousal underlying panic may be entirely wrong for someone whose social anxiety reflects a genuine mismatch between their evolved need for group belonging and their actual social circumstances. A person whose depression is triggered by chronic social entrapment — an exploitative job, a controlling relationship — does not have a simple neurochemical problem that a pill alone can fix; they have a life situation that needs to change. Medicating this person may actually prolong their suffering if it suppresses the signal that would otherwise motivate them to act.
If we could distinguish between these groups, targeting could allow drug efficacy to improve. The modest average effect sizes reported in the literature — the 1.8-point HAM-D difference, the number needed to treat of 7 — might reflect the lumping together of patients who genuinely benefit from medication with patients for whom medication is irrelevant or counterproductive. Separate and test these groups as appropriately distinct and effect sizes comparable to the 80–90% response rates of exposure therapy for phobias (Section 3) might be achievable. Recognising when complementary life changes are required would also allow a more efficient blending of therapy and pharmacy.
Precision psychiatry has been discussed for over a decade, but previous approaches have focused on genetics, neuroimaging, and biomarkers — none of them have used an evolutionary framework to guide phenotyping. The results have been disappointing, precisely because biological markers alone cannot tell you what a symptom is for. Evolutionary sub-typing offers something that genomics and brain scans cannot: a principled, theoretically grounded basis for distinguishing between patients whose suffering is a signal, patients whose defences are miscalibrated, and patients whose neurobiology is genuinely dysfunctional. This could transform psychiatric pharmacology from a one-size-fits-all enterprise into something approaching personalised medicine.
Beyond Symptom Reduction: What Should Drugs Actually Optimise For?
The second major contribution of evolutionary thinking to pharmacology concerns what we measure when we judge whether a drug works. Currently, the regulatory system for psychiatric drugs — from clinical trials to FDA and MHRA (Medicines and Healthcare products Regulatory Agency) approval — is built almost entirely around symptom reduction. A drug for depression is judged by whether it reduces scores on the Hamilton Depression Rating Scale. A drug for schizophrenia is judged by whether it reduces the frequency of hallucinations or delusions. A drug for autism is assessed by whether it diminishes “repetitive behaviours” or improves “social interaction” as measured against neurotypical norms. The assumption is that symptoms are the disease; reduce the symptoms, and you have treated the patient.
An evolutionary perspective calls this assumption into question. If many psychiatric symptoms function as evolved responses rather than simple malfunctions — or, in the case of neurodevelopmental conditions like autism, expressions of natural human cognitive variation — then symptom reduction is an inadequate and sometimes misleading measure of whether a patient is actually doing better. The real question is not “are the symptoms reduced?” but “is this person living a meaningful, functional, and fulfilling life?”
There is an irony here. The DSM-5 itself requires, for virtually every psychiatric diagnosis, that symptoms cause “clinically significant distress or impairment in social, occupational, or other important areas of functioning.” Functional impairment is baked into the very definition of a psychiatric disorder. Yet in practice — and especially in the design of drug trials — this criterion is largely ignored. Trials measure whether symptoms decrease on a rating scale, not whether the patient’s life actually improves. A patient whose HAM-D score drops from 22 to 15 is counted as a responder, regardless of whether they are now able to work or maintain relationships. The diagnostic system acknowledges that what matters is functioning; the treatment system measures only symptoms. This disconnect — between how disorders are defined and how drugs are tested — is one of the most consequential oversights in modern psychiatry.
The evidence that these are different questions is substantial. Research on recovery in psychosis has drawn a careful distinction between clinical recovery (symptom remission and functional improvement as assessed by clinicians) and personal recovery (the person’s own sense of living a meaningful life despite their condition). Leamy and colleagues’ systematic review identified five core processes in personal recovery: Connectedness, Hope, Identity, Meaning, and Empowerment (the CHIME framework). A meta-analysis of the relationship between clinical and personal recovery in schizophrenia spectrum disorders found that the two are only weakly correlated: many patients who achieve symptom remission do not experience personal recovery, and — crucially — some patients who retain residual symptoms report living rich, purposeful, and meaningful lives.
The implications for autism are equally striking. Quality-of-life research consistently finds that autistic people’s wellbeing is predicted not by symptom severity but by employment, relationships, and social support. A capabilities approach — which evaluates whether a person has the opportunities and support to live the life they value, rather than how closely they conform to neurotypical norms — has been proposed as a fundamentally more appropriate framework for understanding autistic adulthood.
Concentrating on functional outcomes rather than symptoms themselves aligns with the evolutionary perspective that many symptoms and spectrums of mental disorder are related to functional traits or systems which occasionally cause suffering or disability. It also has direct consequences for drug development and regulation. If the only endpoints regulators accept are symptom-reduction scores, then the entire pharmaceutical pipeline is optimised for producing drugs that suppress symptoms — regardless of whether symptom suppression actually makes patients’ lives better. A drug that reduced hallucination frequency by 30% but did nothing for occupational engagement, social connection, or subjective wellbeing would pass regulatory scrutiny. A drug that produced modest symptom changes but dramatically improved patients’ capacity to hold a job, maintain relationships, and experience meaning in their lives would struggle to demonstrate efficacy under current criteria.
The current system which equates symptoms with dysfunction constrains innovation. It channels billions of dollars of pharmaceutical research toward a narrow definition of success that is neither scientifically nor ethically justified. The assumption that psychiatric symptoms are the disorder — that reducing them is synonymous with helping the patient — is precisely the kind of unexamined premise that evolutionary thinking can help challenge. Very few psychiatric conditions are simple diseases in the “broken brain” sense. Most involve complex interactions between evolved psychological systems and environments that those systems were not designed for. Treating them as though symptom scores are the whole story of the disease has potentially held back the potential for innovation for decades.