The book’s ‘message is as compelling as it is important: the social costs of mental illness are terribly high and the costs of effective treatments are surprisingly low'.  Daniel Kahneman (psychologist and Nobel economics laureate).

In due course this Penguin is likely to become fashionable – like The Sprit Level and Capital in the Twenty First Century – because it touches issues which many people care deeply about while offering some solutions.

Its message is simple.

* Mental illness is widespread; on some measures it is the largest single source of illness.

* Despite its extent, the public health system pays insufficient attention to mental illness.

 * While the neglect might have been justified in the past by there being only limited effective treatments, today there are Cognitive Behavioural Therapies (CBT) with proven efficacy.

* Not only do CBT often work but they are cost-effective so that the benefits they generate exceed the costs of applying them; often cost savings to the government alone exceed the costs.

* The policy conclusion is that the public health system should make CBT available to all of those for whom they may work (once there are sufficient qualified therapists).

* The book also argues, less rigorously, for preventative measures.

The eminent authors (Layard is a leading labour economist, Cameron a professor of psychology) are also very supportive of the British IAPT (Improving Access to Psychological Therapies) initiative. Between its initiation in 2008/9 and 2012/3 it increased annual numbers seen by a factor of 15, the numbers treated by 38.

Not being a psychologist, I am cautious about commenting on CBT. As best as I can judge, its theory argues that some mental distress generates negative feedback loops which intensify the distress, and that ‘talk therapies’ can often replace these negative loops with positive ones, thereby reducing the degree of distress. (The authors observe that sometimes the medication and CBT applied together is even more effective.)

As well as reduced distress there would be reduced spending on other health care, increased work productivity, and reduced public spending on social services and justice. So the widespread application could be (largely) self-funding in public sector terms. Their cost-effective partly arises because the time required for therapy is limited – an average of ten hours of one-on-one sessions. (The authors emphasise that the therapists have to be properly trained. They mention a British need for about 8000 therapists – which translates to about 400 for New Zealand.)

 I valued the book for its dummies’ guide to mental illness (necessary because it is written for the general public) and for its passionate demand for better treatment for the mentally ill,

It turned out that full economic evaluations were unnecessary because the treatments were so cost-effective that many of the benefits associated with successful treatment could be ignored and yet the treatments were still viable. The thesis is evident in the two most economic chapters.

 Chapter 6 – essentially amounts to a cost-of-illness study – reviews the economic costs of mental illness:

 – unemployment, absenteeism and presenteeism (‘less effective work when a person’s mind is a mess’).The majority of the mentally ill are of working age, so these effects are more important than for some other health issues.)

 – much of the crime in advanced countries is committed by people with a prior-diagnosis of conduct disorder.

 – mental health problems often make physical health worse, typically increasing mortality by 50% for people with the same initial health conditions.

It estimated that the three components cost the British economy 7 percent of GDP (of which 4 percent of the GDP is borne by the Treasury – i.e. taxpayer). In contrast, spending on mental health care amounts to 1 percent of GDP (most of which is borne by the Treasury/taxpayer). The difference between the 7 (or 4) percent and the 1 percent does not, in itself, prove a case for more spending on mental health treatment, That depends on each treatment’s effectiveness and the economic impact of the treatment,

Chapter 11 gathers together a number of studies which measure the gains from reducing mental illness .

The most comprehensive study evaluates the cost of treatment in comparison with QALYs (Quality Adjusted Life Years) a measure of patient wellbeing. The book cites four examples:

 – Depression: CBT compared with a placebo costs £6,700 to give one QALY;

 – Social anxiety disorder: CBT compared to Treatment As Usual (TaU) costs £9,600 to give one QALY;

  – Post-natal depression: Interpersonal therapy compared with TaU costs £4,500 to give one QALY;

  – Obsessive-Compulsive Disorder: CBT compared with TaU costs £21,000 to give one QALY.

The authoritative British National Institute for Health and Care Excellence (NICE) considers that interventions costing the NHS less than £20,000 per QALY gained are cost-effective. (Those costing between £20,000 and £30,000 per QALY gained may also be deemed cost-effective, if certain conditions are satisfied; covered in next paragraph). That means that three of these particular cases are very cost-effective compared with many treatments of physical conditions in the British health system considered worthwhile doing. (The fourth is probably cost-effective.)

The NICE approach focuses only upon the cost to the health system. The cost-effectiveness from a social perspective is generally lower. There may be substantial gains to the public sector in terms of lower social welfare costs and higher tax returns from more of the treated returning to the workforce and from higher productivity at work. (Additionally there may be gains from reduced crime, but thus far they have not been evaluated.) From the even wider perspective of the economy as a whole there will be greater gains from additional production.

Moreover, the measured QALY/wellbeing gains are only those to the individual. Mental illness can also generate considerable distress to the family and associates of the ill. Neither are taken into account.

Such caveats suggest the denominator (QALYs) of the cost-effective ratio are higher than reported above, and the numerator (costs) are lower, so the ratio from the social perspective is even more favourable than that reported for the health perspective of the NICE guidelines.

In summary the use of CBT is being judged as cost-effective on narrow measures, and is almost certainly even more cost effective if a wider perceptive is taken into account.

The book makes a compelling case for taking mental illness more seriously than, apparently, the British health system does; the New Zealand health system is even further behind. This is not only because mental illness is widespread, affecting much of the population directly, or through association, but because there appear to be effective (and cost-effective) treatments which are not being widely applied.

So a very readable book which is likely to have a considerable impact on public perceptions when it becomes more widely known. However, professionals will need to be more cautious than the general public. CBT is not always successful (even when professionally exercised) and the evaluation of their cost-effectiveness is complex.