The UK landed 70th out of 71 for overall mental wellbeing, earning an average score of 49, classifying the UK as enduring - comparatively low compared to the average global score of 65.
The report found that UK mental wellbeing levels in 2023 had not recovered from pre-pandemic levels, according to researchers at the US-based Sapien Labs think tank.
35 per cent of respondents in the UK said they were struggling with their wellbeing.
Whilst wellbeing for those over 65 has remained steady, 18-24-year olds across eight English-speaking countries' mental health has shown the least improvement since 2020.
Also struggling are young adults and poorer families who have endured two economic recessions in just four years, the cost of living crisis and rising rent and house prices.
Another issue making Brits miserable is the lack of trust for political leaders, such as chaos in Westminster, changing prime ministers and partygate.
Across all age groups, the study found that eating extra-processed goods results in much worse mental wellbeing.
60 to 70 per cent of food eaten in the UK is extra processed, with over half of Brits eating it daily reported feeling distressed, compared to 18 per cent who rarely or never do.