What Does Happiness Have to Do with Back Pain?
I don't know what happiness is.
When I get a box of chocolate turtles, I'm happy.
When the turtles are all gone, I'm unhappy.
(Katherine Hepburn)

Whatever happiness is, we know that it is linked to our general feelings of health and well-being. In this study, Japanese researchers tried to find out if low back pain is linked with happiness as well as function, general health, and social activities. They found some of these factors were linked to back pain. Some were linked to each other, but not to back pain directly.

The results of this study show that function is affected most by general health. Happiness and enjoying social events are closely linked to physical health. Since function is linked with how severe the back pain is, then general health must have an impact on back pain.

The authors also reported that a patient's happiness is linked with health status. The authors suggest using happiness, general health, and social activities as measures of outcome for people with back pain. This may help predict who will get better after an episode of low back pain.
References
Yoshiaki Takeyachi, MD, et al. Correlation of Low Back Pain with Functional Status, General Health Perception, Social Participation, Subjective Happiness, and Patient Satisfaction. In Spine. July 1, 2003. Vol. 28. No. 13. Pp. 1461-1467.