The Forbidden Zone and Individual Variation

Among some adults, there appears to be a circadian period of high arousal between about 8-10pm.  This has been called the ‘forbidden zone’ because it is difficult for well-rested adults to easily fall asleep during those hours.  Also, lab investigations suggest that some infants may have a forbidden zone between 5-8pm.  Is this observation of a forbidden zone in some infants, incompatible with my general suggestion to strive for early bedtimes based on drowsy signs?


Some infants, during the first few months, especially around 6 weeks of age, and especially in the evening, quietly whine or whimper or fuss for no apparent reason.  Others have mild to moderate crying bouts. A minority of infants (about 20%), during the first 2-4 months, have intense, prolonged, or inconsolable crying spells in the evening and they often have difficulty easily falling or staying asleep.  Among infants, there is individual variation in a graded fashion in the amount of fussing and crying and the amount of sleeping.  This association of increased crying and decreased sleeping in some infants may, or may not, be related to individual variation in the degree of arousal in the evening hours (the ‘forbidden zone’).  So, trying for an early bedtime is worthwhile, but it might be easier to obtain in some infants than others.

My Blog emphasizes general principles.  Also, a goal of my book, Healthy Sleep Habits, Happy Child, is to focus on the fundamentals of children’s sleep.    However, because of individual variation (Blog Post 14) at any specific age range and variations due to age differences, it is possible to discover what incorrectly appears to be inconsistencies in my advice (see above).   Obviously, all general principles and all fundamental concepts do not always apply equally to all children at all ages. 

My advice is to focus on what is most helpful for your family and do what works best for your child.  Even if you might be confused about some apparent discrepancy in my Blog or book, don’t let that interfere with paying most attention to the sleep basics that work for you, your family, and your child.

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