Ok this can be a tricky one to fix permanently. I would like to get some more info from you. Where are the crack(s)? Do they run from the top corners of the door upward and out at an angle? Ususally cracks in drywall (serious ones at least.) start in the corners. Is the crack across the door in the middle some where? Since you mentioned a condo do you know if the framing in your walls is wood or metal studs? 50% of the reason you have the crack is due to humidity in the room. In the summer the humidity is higher and thus everything expands. In the winter things dry out therefore the static shock in our blankets and the chapped lips. This is the reason your crack appears in the winter. The other 50% is the framing behind that crack. You have movement in some form of the framing materials behind the drywall that is causing the crack. A cheap fix is to pick up a bag of durabond 30minute mud. This material sets harder and faster than typical drywall mud. You should also pick up some plastic mesh drywall tape (the widest you can find). Put a bed of durabond on the crack, install the strip of mesh and then install a second layer of durabond over the mesh. This is the cheaper bandaid approach that may work. The true fix is to remove the drywall and trim around the door and look at the framing to figure out how to stop the movement that is causing the crack. Metal straps may be the answer to fixing the framing, it just may need additionally nails or bracing. Hard for me to say. After fixing the framing you can then sheet rock the wall back, mud and tape the joints, sand and paint. Much more tedious but it is really the best way to fix your delima.
Ok it is a stress crack due to shifting of the walls. Go to Home Depot and look near the lumber section. You will see a "Simpson" strap section. Pick up a couple of 18" flat straps.
Get maybe 4 straps. Run two vertically on each side of the door after removing the sheet rock and door trim. I would place one as close to the door frame as possible, and perhaps space the other one out maybe 4-8" away from the first one if you can, sometimes like the picture below there is not a stud there to nail one to. Run the strap from about 10 - 12" above the door frame down the wall ideally all the way up to the horizontal top plate if you can and come down the studs on each side of the door. The strap will have lots of holes for nails per the picture. Put a nail in every hole. This should stop the shearing effect you are getting. Once done Sheetrock and install the trim back on the door.