First of all, we must remember that Stalin was in power in the Soviet Union for a long time and many different global conditions existed during that time. Stalin took power in the mid-1920s and held it until his death in 1953.
Second, the greatest economic and political turmoil under Stalin probably came from his own actions, not from outside economic conditions. The Soviet Union really did not suffer from the Great Depression. However, there were food shortages due to internal conditions and this led Stalin to force the collectivization of agriculture. This action had tremendous consequences as millions of peasants moved to cities and a terrible famine ensued with the loss of millions of lives.
This was the time of greatest turmoil in the Soviet Union and historians do not really say that it was caused by global economic conditions.