June Gruber at Edge.org:
We know a lot about negative emotions in psychopathology, which has been important in getting to the root of disorders such as anxiety, substance abuse, and depression. This knowledge has been effectively disseminated in order to develop etiological models and create effective treatment. We know far less about the role of positive emotions in human health and also human dysfunction, which is one of the biggest questions that I've been trying to tackle lately. It's not a trivial question.
Why should we care about the fact that studying positive emotions has been absent in our understanding of severe and chronic mental illness? There're two broad reasons as to why this question matters and why I've been spending time thinking about it. One of them is a practical reason and one of them is a more theoretical reason. The practical reason we should care about positive emotions in our conceptualizations of human health and severe mental illness is because, to put it plainly, severe and chronic psychiatric diseases are a societal burden. We know that, for example, substance use disorders alone are accounting for $500 billion a year in annual cost. Anxiety disorder is not far behind in terms of cost relating to days missed in work productivity and healthcare utilization. We also know that many common and chronic disorders—depression or bipolar disorder—are in the top ten causes of leading worldwide disability.
More here.