Six years ago, K. Walhbeck¹ proposed in this journal that “the evidence base for public mental health interventions is convincing and the time is now ripe to move from knowledge to action”. Unfortunately, the field of public mental health has moved too slowly. Indeed, the scholarly review by Fusar‐Poli et al² concludes that “prevention of mental disorders in young people has not yet solidified as global research or programmatic focus”.

Prevention has a long history in medicine, with early successes such as the use of lemons by J. Lind in 1747 to prevent scurvy in the British Navy, and J. Snow's removal of the handle of the Broad Street water pump in 1854 to prevent the spread of cholera in London. There have also been notable advances in prevention of neuropsychiatric disorders. One hundred and fifty years ago, patients with neurosyphilis, such as F. Nietzsche, occupied thousands of beds in mental hospitals. More recently, the toxic effects of phenylketonuria were neutralized by phenylalanine‐free diet, and the threatened epidemic of AIDS‐related dementia was averted by the development of effective medicines for HIV.

Public health approaches are common in medicine. Mass X‐ray screening for tuberculosis was highly effective, and indeed one of us (RMM) was diagnosed, while a Glasgow medical student, as having early tuberculosis by such a screening campaign. Cardiologists, faced with an epidemic of fatal myocardial infarction in the mid 20th century, realized that treatment with ever‐more expensive interventions was not reducing prevalence; influenced by epidemiologists such as G. Rose, they turned their attention to prevention. Tackling the risk factors for coronary artery disease (such as poor diet, high blood pressure, high cholesterol and smoking) has led to dramatic reductions in the prevalence of myocardial infarction. Similarly, oncologists have long embraced screening and prevention of lung cancer by reducing tobacco smoking in the general population, and now hepatologists are realizing that they cannot continue to treat end‐stage liver disease without tackling the root cause – alcohol.

Why has psychiatry lagged so far behind other specialties in embracing a preventive approach? It has not always been like this. During the period of psychoanalytic supremacy, from the 1940s to the 1970s, psychiatrists commonly gave advice on how to improve mental health, for instance by more liberal child rearing practices. Indeed, A. Gregg told the American Psychiatric Association in 1944: “there will be applications [of psychiatry]… to the human relations of normal people – in politics, national and international, between races, between capital and labor, in government, in family life, in education, in every form of human relationship, whether between individuals or groups”³.

With the decline of psychoanalysis, how­ever, psychiatry retrenched to the clinic and the idea of prevention disappeared from view. The Decade of the Brain from 1990 to 1999 had a primary focus on “brain research”, with ever more sophisticated neuroscience, imaging and genetic techniques. But im­proved knowledge of how the brain “works” did not lead to a reduction in prevalence of mental illness.

As outlined by Fusar‐Poli et al, the re‐emergence of interest in prevention in psychiatry came with indicated prevention, in the form of early intervention units for first episode psychosis. These have been shown to improve patient health and to be cost‐effective. Subsequently, selective prevention in the form of “at risk mental state” services was proposed by McGorry and Yung in Australia, and enthusiastically adopted by academic centres in the US and Europe. The “at risk mental state” paradigm has brought a fresh way of thinking about prevention of mental illness, and, as Fusar‐Poli et al note, has now expanded to subsume a transdiagnostic approach and a focus on youth mental health in general. Sadly, this approach has not resulted in the hoped‐for reduction in incidence of psychotic disorders, as the service model reaches only a minority of those indivi­duals who will ultimately develop psychosis⁴.

Psychiatry needs to move “upstream” and identify possible candidates for selected prevention in childhood, such as subclinical psychotic experiences, developmental delays, psychological and behavioural problems, or family history of mental illness. Focusing on children with a combination of these risk factors, or possibly combining them with biological measures, has potential for intervention. But how to intervene? It has been suggested⁵ that “fostering self‐esteem, improving parent‐child relationships, promoting secure attachment relationships with trusted others, increasing social and neighbourhood supports, and reducing bullying all play a part in improving outcomes”. The evidence is there, but psychiatry cannot act alone to implement such broad‐ranging measures, and needs “buy‐in” from policy makers.

In medicine, universal primary prevention has been shown to be more cost‐effective than developing “high‐tech” treatments for those with established disease. Persuading the general public not to smoke tobacco has saved many more lives than operating on those with lung cancer or thrombotic coronary arteries. Do we have equivalent opportunities to prevent mental disorder by diminishing population exposure to risk increasing factors? Fusar‐Poli et al raise the possibility of reducing mental illness by developing more equitable societies, and point to the high rates of mental disorder in inner cities. High population density, greater exposure to stress, pollution and crime, and lack of green space have all been suggested as responsible for the psychotoxic effect of urbanicity. Although urban planning is beyond the expertise of mental health professionals, we can convince policy makers, by presenting the evidence, that there is an urgent need to re‐engineer our cities to improve public mental health.

When examining individual‐level risk factors, the best‐replicated risk factors in the field of psychosis are obstetric events, child abuse, migration, adverse life events, and heavy cannabis use⁶. Improved perinatal care, supporting positive parenting, and reducing poverty and income inequality can pay dividends for future generations⁷. But there is an urgent need to address one risk factor which is increasing rapidly in both strength and prevalence – cannabis use.

The worldwide trend towards increasing use of cannabis, especially of high potency varieties, cries out for a preventive approach⁸. A trans‐European study estimated that, in London and Amsterdam, 30% and 50% of new cases of psychosis, respectively, would be prevented if no one smoked high‐potency cannabis. The risk of developing psychotic disorder was increased 5‐fold in those with daily use of high‐potency cannabis compared with those who did not use cannabis⁸. This is a similar effect size as between asbestos and lung cancer, but the outcome is much earlier in life. We cannot just wait in our units and emergency departments to treat the increasing numbers of young people with cannabis‐related psy­chosis. There is much to learn from the pub­lic education programme implemented in Iceland over the last 20 years, with remarkable decreases in rates of alcohol consumption and tobacco and cannabis smoking among young people⁹.

It is time for mental health professionals to speak up about the risks of heavy use of cannabis on rates of psychosis and other mental health problems. It is time to move out of the clinic, remove the handle from the pump, and embrace the challenge of public health psychiatry.

六年前，K. Walhbeck ¹在该期刊中提出，“公共心理健康干预措施的证据基础令人信服，现在从知识转向行动的时机已经成熟”。不幸的是，公共心理健康领域进展太慢。事实上，Fusar‐Poli 等人²的学术评论得出的结论是，“年轻人精神障碍的预防尚未成为全球研究或规划重点”。

预防在医学上有着悠久的历史，早期的成功例如 J. Lind 在 1747 年使用柠檬来预防英国海军的坏血病，以及 J. Snow 在 1854 年拆除了 Broad Street 水泵的手柄以预防坏血病。霍乱在伦敦蔓延。在预防神经精神疾病方面也取得了显着进展。一百五十年前，像尼采这样的神经梅毒患者占据了精神病院的数千张床位。最近，不含苯丙氨酸的饮食中和了苯丙酮尿症的毒性作用，并且有效治疗艾滋病毒药物的开发避免了艾滋病相关痴呆症的流行威胁。

公共卫生方法在医学中很常见。大规模 X 射线结核病筛查非常有效，事实上，我们中的一名格拉斯哥医科学生（RMM）通过这种筛查活动被诊断出患有早期结核病。心脏病专家在 20 世纪中叶面临致命性心肌梗死的流行时，意识到采用越来越昂贵的干预措施进行治疗并不能降低患病率；受到 G. Rose 等流行病学家的影响，他们将注意力转向了预防。解决冠状动脉疾病的危险因素（如不良饮食、高血压、高胆固醇和吸烟）已导致心肌梗塞患病率大幅降低。同样，肿瘤学家长期以来一直主张通过减少普通人群吸烟来筛查和预防肺癌，现在肝病学家意识到，如果不解决根本原因——酒精，他们就无法继续治疗终末期肝病。

为什么精神病学在采用预防方法方面远远落后于其他专业？但情况并不总是这样。在精神分析至上的时期，从 20 世纪 40 年代到 1970 年代，精神科医生通常就如何改善心理健康提出建议，例如通过更自由的育儿方式。事实上，A. Gregg 在 1944 年告诉美国精神病学协会：“[精神病学]将会应用于……普通人的人际关系——在政治中、国内和国际上、种族之间、资本和劳工之间、政府中、社会中。”家庭生活、教育、各种形式的人际关系，无论是个人之间还是群体之间” ³ 。

然而，随着精神分析的衰落，精神病学缩减到临床，预防的理念也从视野中消失。 1990 年至 1999 年的“大脑十年”主要关注“大脑研究”，神经科学、成像和遗传技术变得更加复杂。但对大脑如何“工作”的了解的提高并没有导致精神疾病患病率的降低。

正如 Fusar‐Poli 等人所概述的，精神病学中对预防的兴趣重新出现，伴随着有针对性的预防，即针对首发精神病的早期干预单元。这些已被证明可以改善患者健康并且具有成本效益。随后，澳大利亚的 McGorry 和 Yung 提出了以“处于危险心理状态”服务为形式的选择性预防，并被美国和欧洲的学术中心热情采用。 “处于危险心理状态”范式带来了预防精神疾病的新思维方式，并且正如 Fusar-Poli 等人指出的那样，现在已经扩展到包含跨诊断方法和对青少年心理健康的总体关注。遗憾的是，这种方法并没有达到预期的减少精神障碍发病率的效果，因为服务模式只覆盖到最终发展为精神病的少数人⁴ 。

精神病学需要向“上游”发展，并确定儿童时期进行选择性预防的可能候选对象，例如亚临床精神病经历、发育迟缓、心理和行为问题或精神疾病家族史。关注具有这些危险因素组合的儿童，或者可能将其与生物措施相结合，具有干预的潜力。但如何干预呢？有人建议⁵ “培养自尊、改善亲子关系、促进与信任他人的安全依恋关系、增加社会和邻里支持以及减少欺凌行为都有助于改善结果”。证据是存在的，但精神病学无法单独采取行动来实施如此广泛的措施，需要政策制定者的“支持”。

在医学领域，事实证明，普遍的初级预防比为已患疾病的人开发“高科技”治疗方法更具成本效益。说服公众不要吸烟比对肺癌或血栓性冠状动脉进行手术挽救了更多的生命。我们是否有同等的机会通过减少人们接触风险增加因素来预防精神障碍？ Fusar-Poli 等人提出了通过发展更加公平的社会来减少精神疾病的可能性，并指出内城区精神疾病的高发病率。高人口密度、更大的压力、污染和犯罪以及缺乏绿色空间都被认为是城市化的精神毒害效应的原因。尽管城市规划超出了心理健康专业人士的专业知识，但我们可以通过提供证据来说服政策制定者，迫切需要重新设计我们的城市以改善公众心理健康。

在检查个人层面的风险因素时，精神病领域复制得最好的风险因素是产科事件、虐待儿童、移民、不良生活事件和大量使用大麻⁶ 。改善围产期护理、支持积极养育子女以及减少贫困和收入不平等可以为子孙后代带来红利⁷ 。但迫切需要解决一个风险因素，即大麻的使用，这一因素的强度和流行率都在迅速增加。

全球范围内越来越多地使用大麻，尤其是高效品种大麻，迫切需要采取预防措施⁸ 。一项跨欧洲研究估计，在伦敦和阿姆斯特丹，如果没有人吸食高效大麻，则分别可以预防 30% 和 50% 的新精神病病例。与不使用大麻的人相比，每天使用高效大麻的人患精神障碍的风险增加了 5 倍⁸ 。这与石棉和肺癌之间的效应大小相似，但其结果要早得多。我们不能只是在我们的科室和急诊科等待治疗越来越多患有大麻相关精神病的年轻人。冰岛过去 20 年来实施的公共教育计划有很多值得学习的地方，年轻人中饮酒、吸烟和吸食大麻的比率显着下降⁹ 。

现在是心理健康专业人士谈论大量使用大麻对精神病和其他心理健康问题发生率的风险的时候了。是时候走出诊所，取下泵的手柄，接受公共卫生精神病学的挑战了。