See Shyness: How Normal Behavior Became a Sickness by Christopher Lane. It now has a DSM entry as "Social Anxiety Disorder" and Paxil is shilled for it.

It's not just the DSM, either -- drug ads to psychiatrists push this too. See "Do These Drug Ads Offend You?" at The Huffington Post. (The ad in the broken "Hauteur" link is here and the one in the broken "Boiling Rain" link is here. Gotta love their headline: "Ryan is adamant his Scottish descendants tease, taunt and torture him from above. He claims they send boiling "Scottish" rain lashing down to burn his skin.")

And yes, even love can be defined as a mental illness: My favorite example was a 1970's ad for Serentil featuring a Royal Doulton figurine of a woman holding a book and rapt in daydreams. The lead copy read, "There is a brooding quality to this figure. She seems aloof, cut off from reality ... possibly schizophrenic in demeanor." In tiny print at the bottom? "Actual title: Romance." (Alas, I can't find a specimen of the ad, but the figurine is here.)