Psych Central Reviews

Reviews Home » Book Review: The Power of When

Book Review: The Power of When

Just when you think there isn’t anything more to learn about yourself, a self-help book comes along to surprise you with a new way of looking at things. That was the pleasant surprise I received after reading The Power of When, the new book by Michael Breus, Ph.D., that describes and explores chronotypes.

Your chronotype, for those of you unfamiliar, is your internal, biological clock, which helps determine when to sleep, when to wake, when to eat, and when to do a lot of other things that we take for granted in life. Traditional sleep researchers have categorized five different chronotypes, and everybody has one, but Breus was unhappy with the existing set of chronotype measures typically used in research, so he created his own for this book. He even provides an online quiz for anyone to take. Breus’ approach is meant to be more of a fun, let’s explore your chronotype kind of thing (not for research purposes). And to that end, the resulting categories have animal names:

  • Dolphins – Insomniacs who are intelligent, neurotic light sleepers, with a low sleep drive. They wake at the smallest noise.
  • Lions – Morning-oriented driven optimists with a medium sleep drive, who rise early.
  • Bears – Fun-loving, outgoing people who prefer a solar-based schedule (rise and fall with the sun), and who have a high sleep drive.
  • Wolves – Night-oriented creative extroverts with a medium sleep drive.

As Breus points out, the vast majority of people (fifty percent or more) are, like me, Bears. The other three categories pretty equally make up the remaining fifty percent and tend to be less in sync with social norms. He also notes that these groups don’t run on the same bio-time, nor do they have the same metabolism.

The author spends some time ensuring you understand there are no hybrid chronotypes, and you really need to pick the single category that best fits with your actual behaviors. (As some reviewers on Amazon note, however, there are still some people who swear they are in-between types, and so much of the advice given in the rest of the book doesn’t work well for them. And this points more generally to the problem with any type-based system that psychology tries to create, whether it’s based on personality traits or, as in this case, your circadian rhythms.) The next few chapters describe the “perfect day” for each one of these four distinct chronotypes, so that you get a very clear sense of which chronotype you are.

The second part of the book is devoted to major life areas: relationships, fitness, health, sleep, eat and drink, work, creativity, money, and fun. Each chapter is devoted to a deep-dive in each of these sections and talk about the failure, success, and science behind the topic, as well as what each chronotype should strive to do. For instance, in the chapter on sleep, the author discusses waking, napping, sleeping in, and bed times. Each section is well organized, referenced, and puts the topic into context with your bio-rhythms (along with accompany graphs, for those who appreciate visual references).

The idea is that if you follow the advice and formulas that correspond with your chronotype, you’ll live a more fulfilling, healthier, and happier life. You’ll also better understand yourself and others — especially those with a different chronotype than your own. There is so much good advice jammed into this section of the book, I’d recommend buying it for this section alone. Pretty much any question you have regarding your chronotype and daily life activities — when’s the best time to drink coffee? should you sleep in on the weekends? what kinds of things can you do to be more awake during the day? — are answered in these nine chapters.

The third part of the book contains just two short chapters, which feel a bit like after-thoughts, detailing your chronotype’s interaction with seasonal patterns (including a woman’s monthly pattern), and how chronotypes change as we age.

Overall, I found the book to be a well-organized, easy read with a good flow. It should take most people just a few days to read, but it may take longer to digest all the information Breus presents and make the most use of it. I found numerous tips and helpful advice that I’m practicing in my own life today. Make no mistake, though — this book isn’t just about sleep. It’s about how your natural biological, inherited rhythms impact every aspect of your life. The more you understand about this innate clock, the better you’ll understand yourself and the needs that fit best with your own chronotype.

The Power of When: Discover Your Chronotype—and the Best Time to Eat Lunch, Ask for a Raise, Have Sex, Write a Novel, Take Your Meds, and More

Little, Brown and Company, September 2016

Hardcover, 384 pages


Book Review: The Power of When

Psych Central's Recommendation:
Worth Your Time! +++

Your Recommendation: (if you've read this book)
1 Star2 Stars3 Stars4 Stars5 Stars (No Ratings Yet)

Want to buy the book or learn more?
Check out the book on!
(All links to provide a small affiliate fee to us if you decide to purchase the book.)

John M. Grohol, Psy.D.

Dr. John Grohol is the founder & CEO of Psych Central. He is an author, researcher and expert in mental health online, and has been writing about online behavior, mental health and psychology issues -- as well as the intersection of technology and human behavior -- since 1992. Dr. Grohol sits on the editorial board of the journal Computers in Human Behavior and is a founding board member and treasurer of the Society for Participatory Medicine. He writes regularly and extensively on mental health concerns, the intersection of technology and psychology, and advocating for greater acceptance of the importance and value of mental health in today's society. You can learn more about Dr. John Grohol here.

APA Reference
Grohol, J. (2016). Book Review: The Power of When. Psych Central. Retrieved on October 29, 2020, from
Scientifically Reviewed
Last updated: 14 Nov 2016
Last reviewed: By a member of our scientific advisory board on 14 Nov 2016
Published on Psych All rights reserved.