A system configured to deliver sensory stimulation to a user during deep sleep in a sleep session, the system comprising: one or more sensory stimulators configured to provide sensory stimulation to the user during the sleep session; and one or more hardware processors coupled to the one or more sensory stimulators, the one or more hardware processors configured by machine-readable instructions to: obtain historical sleep depth information for a population of users, the historical sleep depth information being related to brain activity of the population of users that indicates sleep depth over time during sleep sessions of the population of users; cause a prediction model to be trained based on the historical sleep depth information by determining the average sleep depth and a probability of a particular sleep stage over time, starting from a time reference which is set to sleep onset, based on the historical sleep depth information, and providing the average sleep depth and the probability of a particular sleep stage over time as input to the prediction model; cause the trained prediction model to output a time dependent predicted sleep stage for the user during the sleep session, the time dependent predicted sleep stage indicating whether the user is in deep enough sleep for stimulation; and cause the one or more sensory stimulators to provide the sensory stimulation to the user based on the time dependent predicted sleep stage over time during the sleep session, the one or more sensory stimulators being caused to provide the sensory stimulation to the user responsive to the time dependent predicted sleep stage indicating the user is in deep enough sleep for stimulation. one or more sensory stimulators configured to provide sensory stimulation to the user during the sleep session; and one or more hardware processors coupled to the one or more sensory stimulators, the one or more hardware processors configured by machine-readable instructions to: obtain historical sleep depth information for a population of users, the historical sleep depth information being related to brain activity of the population of users that indicates sleep depth over time during sleep sessions of the population of users; cause a prediction model to be trained based on the historical sleep depth information by determining the average sleep depth and a probability of a particular sleep stage over time, starting from a time reference which is set to sleep onset, based on the historical sleep depth information, and providing the average sleep depth and the probability of a particular sleep stage over time as input to the prediction model; cause the trained prediction model to output a time dependent predicted sleep stage for the user during the sleep session, the time dependent predicted sleep stage indicating whether the user is in deep enough sleep for stimulation; and cause the one or more sensory stimulators to provide the sensory stimulation to the user based on the time dependent predicted sleep stage over time during the sleep session, the one or more sensory stimulators being caused to provide the sensory stimulation to the user responsive to the time dependent predicted sleep stage indicating the user is in deep enough sleep for stimulation.