Each user session might have one or more tasks running on its behalf where each task might acquire or wait to acquire a variety of resources. The following types of resources can cause blocking that could result in a deadlock.
Causes to Deadlock
LocksWorker threadsMemoryParallel query execution-related resourcesMultiple Active Result Sets (MARS) resources
All the above listed may cause to Deadlock.The default interval is 5 seconds.
If the lock monitor thread finds deadlocks the deadlock detection interval will drop from 5 seconds to as low as 100 milliseconds depending on the frequency of deadlocks.
If the lock monitor thread stops finding deadlocks the Database Engine increases the intervals between searches to 5 seconds.
You can find some more information regarding Deadlock