Substance use disorder occurs when a person needs alcohol or another substance (drug) to function normally. Abruptly stopping the substance leads to withdrawal symptoms. Addiction means that a person has a strong urge to use the substance and cannot stop, even if they want to.
So it is important to maintain positive nitrogen balance in the body while sleeping. When you do and conditions are right so that your rate of protein synthesis exceeds your rate of degradation, and you maintain a positive nitrogen balance, you can grow while you sleep.
It actually teaches about the different phases of growth vs. sleep patterns, results of sleep studies in babies and children, effects of crying it out and sleep training, etc. It is wonderful and empowering, and I highly recommend it! On another note, babies grow SO fast!