[ **up: [[Biological rhythms]]** ] --- # Circadian rhythms Circadian rhythms have been widely observed in animals, plants, fungi, and cyanobacteria; there is evidence that they evolved independently in each of these kingdoms of life.[^1] --- ## Circadian rhythms and reproduction There have been very studies on correlation between circadian rhythms and [[Reproduction and sex]].[^1] [[2024-0815. Clock genes play a primary role in orchestrating the reproductive processes in mammals.|'However, the discovery of functional molecular clock machinery in reproductive tissues, and the use of clock gene mutant models have revealed that such genes play a main role in orchestrating reproductive processes in mammals.']][^2] --- ## Circadian rhythms and ADHD People with [[ADHD]] can have troubles regulating their circadian rhythm. ### The importance of light and dark - The human body’s internal timekeeper resets each morning with exposure to light. ‘Without enough morning light, the sleep-wake cycle may gradually drift later and later each day, decoupling from the day-night cycle.’[^3] - Darkness also influences the circadian rhythm, since it triggers the secretion of [[Melatonin|melatonin]].[^3] #### Light therapy - Bright light exposure should occur within two hours of natural waking time, and for at least 30 minutes; a morning walk is ideal, but light exposure devices can work for some.[^3] - Furthermore, avoid light exposure before and during sleep; in an ideal world, you’re supposed to be dimming the lights and avoiding screens two hours before bedtime.[^3] Use a sleep mask or install blackout curtains.[^3] - Gradually shift your bedtime (15 mins a day), until your internal clock has been adjusted to sleep and wake at socially typical times.[^3] #### Melatonin supplements - **For circadian shifting:** 3mg dose about six hours before your natural sleep onset; keep adjusting the time as you change your sleep pattern.[^3] - **For sleep-schedule maintenance:** 1-2mg two hours before bedtime.[^3] --- ### Delayed Sleep Phase Syndrome (DSPS) - **Delayed Sleep Phase Syndrome (DSPS)**, a type of circadian rhythm sleep disorder, is often brushed off as poor sleep hygiene (e.g. bedtime procrastination), but is actually quite common among individuals with [[ADHD]].[^3] - DSPS affects the internal body clock, and is characterised by struggling to fall asleep and wake at socially conventional times.[^3] - difficulty getting to sleep at a desired time - a relatively consistent, albeit delayed, time of falling asleep each night - relatively unbroken sleep once initiated - difficulty waking at a desired time - an inability to correct delayed sleep-wake patterns by scheduling sleep and wake times - Many people with DSPS will stay up very late at night to get their tasks done (thereby also exposing themselves to a lot of artificial light, which further affects the circadian rhythm), and only go to bed at very early hours in the morning when the sleepiness kicks in. - Other people with DSPS will go to bed dutifully at the ‘correct’ time, only to lay awake for hours, waiting to finally fall asleep. - The result of both approach is struggling with mornings, and generalised sleep-deprivation.[^3] - **DSPS vs insomnia:** Insomniacs struggle to fall asleep, while those with DSPS struggle to fall asleep at *socially conventional times*. Insomniacs also often struggle with staying asleep.[^3] - **DSPS vs bedtime procrastination:** key difference is that those with bedtime procrastination are putting off falling asleep at socially conventional times… but they *could* fall asleep then if they weren’t procrastinating! They will often feel sleepy while they’re reading/doomscrolling/doing whatever it is they’re doing instead of sleeping.[^3] [^1]: ‘Circadian rhythm’, *Wikipedia*, updated 1 July 2024, https://en.wikipedia.org/wiki/Circadian_rhythm. [^2]: Mario Caba, Gabriela González-Mariscal and Enrique Meza, ‘[[Caba, González-Mariscal & Mesa. ‘Circadian Rhythms and Clock Genes in Reproduction_ Insights From Behavior and the Female Rabbit’s Brain’, 2018.|Circadian Rhythms and Clock Genes in Reproduction: Insights From Behavior and the Female Rabbit’s Brain]]’, *Frontiers in Endocrinology* 9, Article 106 (March 2018), p. 1. [^3]: Alex Mortlock, ‘Late Nights, Later Days: The Under-Recognized Impact of Delayed Sleep Phase Syndrome in ADHD’, *[['ADDitude Magazine'|'ADDitude Magazine']],* updated 21 May 2024, https://www.additudemag.com/delayed-sleep-phase-syndrome-signs-treatments-adhd/.