In the primary repression phase, 'it is highly probable that the immediate precipitating causes of primal repressions are quantitative factors such as...the earliest outbreaks of anxiety, which are of a very intense kind'.
1 A psychiatrist treats mood disorders, such as anxiety and depression, which can contribute to sleep problems. Psychiatrists may conduct therapy and prescribe medication to relieve symptoms.  A psychologist provides psychotherapy to treat mood disorders that can interfere with sleep.
Sleep studies help doctors diagnose sleep disorders such as sleep apnea, periodic limb movement disorder, narcolepsy, restless legs syndrome, insomnia, and nighttime behaviors like sleepwalking and REM sleep behavior disorder.