You might not know it to look at them, but Erin Silver (Jessica Stroup) and Britney Spears have a lot in common.

According to E! Online's Kristin Dos Santos, Kelly's younger sister will be the focus of a serious story line when 90210 comes back from hiatus in January.

Silver will be diagnosed with bipolar disorder, as the show aims to focus on more relevant teen issues upon its return.

We hope this doesn't mean the character will shave her head and/or attack any vans with an umbrella.

Matt Richenthal is the Editor in Chief of TV Fanatic. Follow him on Twitter and on Google+.