Some of this is due to the difference in indoor humidity and some is due to the "rising truss" phenomenon which causes the ceiling structure to go up and down. Also a change in the heating system design sometimes causes cracks associated with changes in temperature or humidity, or even (and more common) is failure to properly secure drywall sheets to the wall studs. This causes movement between two sheets and cracking along the joints between them.
The good news is that drywall cracks are fairly easy to fix. The bad news is that if you donít address the cause of the problem (for example, if the drywall is not better secured to the studs) it may become a recurrent problem.