Federal Judge Richard Berman announced the sentence Tuesday after hearing the actor's son apologize and admit that he had squandered a lot of opportunities to turn his life around.
The judge said earlier that he did not have confidence that Douglas would turn his back on drugs after pleading guilty in January to drug charges.
The troubled 31-year-old son of the Academy Award-winning actor admitted to dealing methamphetamine and cocaine.
He was believed to be facing a minimum prison 10-year term.
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