SQL- find overlapping prescriptions

I have a bunch of patient prescriptions, each having a certain start date and an end date. I would like to find the instances where a patient has been taking more than one drug (at the same time) in the same drug category for more than 2 days. duration  should overlap.

Table structure looks like this:

PatientID  StartDate  EndDate    Drug        DrugCategory
001        1/1/2013  1/5/2013   A           Cat1
001        1/1/2013  1/4/2013   B           Cat1
001        1/10/2013   1/12/2013   C           Cat1
002     .......   ........   ............. .........

In the sample code above, Patient 001 was prescribed 3 drugs in the same category and the first two drug overlapped in duration more than 2 days. So, I would like the query return the first two records.

Hope someone can help. This is using SQL Server 2008 R2 btw.