Stress cracks in walls are generally caused by the home's foundation settling unevenly. (Ceiling cracks are generally caused by detachment of the plaster system from the framing. Read more about that here)
The most common place for them to appear is at the top and bottom of doors and windows, particularly near the corners.
While many homes will settle within the first decade of the home's life, some continue to settle because of aggravating causes, primarily water softening the soil at the foundation.
How can you determine if you have foundation problems? One sure tell-tale sign is the presence of 'step cracks' in the brick foundation or exterior.
If these cracks (usually following a mortar joint) are present, a call to a foundation company to evaluate is your best bet. If foundation issues are addressed, our repair is generally permanent.
While stress cracks in walls cannot always be prevented, following a general protocol of proper preparation, appropriate materials and plaster anchors gives you the best and longest lasting repair.