A good laugh is sunshine in a house.

William Makepeace Thackeray (1811-1863) English novelist

“On Love, Marriage, Men, and Women,” Sketches and Travels in London (1856)
    (Source)

This particular line is widely attributed to Thackeray, but rarely cited. Part of the problem is that it is almost always given as "A good laugh is sunshine in the house," rather than "a house."

It is also sometimes cited to his famous novel Vanity Fair (1848), though the quotation cannot be found there.