According to a recent survey (yes, another one!), the UK was voted the second most miserable place. In fact, countries with humanitarian crises fared better than the UK. The general trend of the survey found that wealthier countries fared comparatively poorly, so having access to more money and living in an economically stable country were not necessarily factors that made people happier. However, the report's results may be skewed because only internet-enabled respondents could participate and due to language restrictions, large populations were excluded from the survey. More in our article: What is the mental state of the world right now?
Despite being a developed country, it ranks as the second most miserable place in the world according to that survey. And you’re right, wealth and economic stability don’t always correlate with happiness.
It's also a question of the conditions of living: when there is little solidarity and a widening gap between fringes of the population used to live together in the past, people get more depressed.
