I don't know if any of this is correct.

From Republicans Are Happier Than Democrats by Audacious Epigone.

I really quite dislike the point scoring that goes on trying to identify some metric by which Democrats compare favorably to Republicans (or vice versa).  It is usually based on shallow and non-robust research with multiple other failings.

But this one is interesting because it is stable over time and a large sample size.  

It’s nothing new. Since it’s inception, the General Social Survey has inquired about respondents’ self-reported personal happiness. In every single year, Republican happiness has averaged higher than Democrat happiness has:

Click to enlarge. 

It doesn’t seem to track much with which party controls the White House, one of the few things about the contemporary United States that would make the nation’s founders happy. During Republican presidential administrations, Republicans have a net happiness score averaging 14.1 points higher than Democrats. During Democrat presidential administrations, Republicans’ net happiness score averages 12.4 points higher than that of Democrats, a modest difference.

Looking at congressional control might reveal a stronger correlation. In 2012, during the heyday of the Tea Party, for example, Republican happiness shoots up while Democrat happiness dips a bit. Notably, TDS isn’t detectable in the 2018 iteration of the survey at all. 

Accepting the premise that this is something real, I am struck that the gap is so long lasting (nearly fifty years) and how large the gap is.  Usually the effect sizes are small in these sort of partisan comparisons.  Eyeballing the graph, we have Republicans being consistently 50-100% happier than Democrats.

Why?  I am guessing that there are perhaps some demographic dynamics in play.  

Strictly from memory, Republicans tend to be older than Democrats.  Young people often have a higher inclination towards anxiety than older people.  

Republicans tend to be more wedded than Democrats which is usually a positive in terms of psychological health which I presume translates into happiness.

Republicans tend to be more religiously observant than Democrats.  Religion can frequently provide context and promise and serve as a buffer when experiencing quotidian as well as painful setbacks.

If we were to look at the trend lines, Republicans are either flat or a very shallow decline in happiness.  Democrats seem to have a much more pronounced decline over the fifty years.  My speculation is that that might be tied to the leftward drift of the Democratic Party.  Several studies have suggested that Republicans have been pretty stable on most the major issues over the years but that the Democratic party has definitively moved to the left.  Since there seems to be a very loose correlation between authoritarianism/blank slate/determinism, perhaps the Democrat happiness results are being driven by a changed ideological make-up of the Democratic Party.

I don't know if any of this is correct.