Cortisol and melatonin: the two opposing players of your day

In the evening on the sofa, your eyes are almost closing. You drag yourself to bed, switch off the light – and are suddenly wide awake. Your mind switches on, and sleep is out of the question. Then in the morning the opposite: the alarm goes off and you feel completely wiped out, even though you actually slept.

What is going on with cortisol and melatonin? These two hormones are the opposing players of your day. Here you will find out what their daily curves look like, what throws them out of sync and what a saliva test can show – and what it can't.

Cortisol and melatonin: two curves, one day

Melatonin is the hormone of darkness. It is produced in the pineal gland, a small gland in the brain. The internal clock gives the starting signal, and light slows down its production. Melatonin sends the body the message "it is night" and sets night-time processes in motion (PubMed 29318587). It rises in the evening, is high during the night and falls in the morning.

Cortisol is the hormone that gets you ready for the day. It starts to rise in the early hours of the morning and reaches its peak shortly after waking up (PubMed 23148157). In the first 30 to 45 minutes after waking up there is another clear rise, known as the cortisol awakening response (PubMed 26563991). Over the day, cortisol then slowly falls and is at its lowest late in the evening.

So being in sync means: lots of melatonin and little cortisol in the evening, and the other way round in the morning. If the curves are shifted, it feels like what is described above.

Does cortisol block melatonin? What is known

You often read that "cortisol inhibits melatonin". What has mainly been shown in humans is that both hormones are controlled by the same internal clock and therefore run in opposite directions. That a high cortisol level in the evening directly slows down melatonin production, on the other hand, has not been clearly shown. Another link is well documented: people with chronic insomnia had more cortisol in their blood over the day, most clearly in the evening and in the first half of the night (PubMed 11502812). Exactly how this works has not yet been clarified.

Melatonin's strongest opponent: light in the evening

What definitely slows down melatonin is light. In a study of 116 young adults, ordinary room light before bedtime made melatonin rise later in 99 percent of participants and shortened the melatonin phase by about 90 minutes. Light during the usual sleeping time lowered melatonin by more than half in most trials (PubMed 21193540).

Screens add to this: people who read on a light-emitting reading device in the evening instead of a printed book had less melatonin, fell asleep later, were less tired in the evening and less alert the next morning (PubMed 25535358).

This fits the pattern of "dead tired in the evening, wide awake in bed": after bright bathroom light and your phone in bed, the "night" signal arrives later.

Melatonin deficiency: symptoms and what lies behind them

"Melatonin deficiency" is not an established medical diagnosis. The amount of melatonin naturally varies greatly from person to person. Symptoms such as difficulty falling asleep or sleep that keeps shifting later are non-specific and have many possible causes.

And with age? Here the studies are not consistent. In a study with saliva samples over 24 hours, the night-time peak in people around 40 was already only about 60 percent of the values of young adults, and even lower at older ages (PubMed 12485366). Another study, by contrast, found no difference between healthy older people taking no medication and young men (PubMed 10569297). So less melatonin in older age is common, but not a law of nature.

Melatonin products: For certain disorders of the sleep-wake rhythm, for example with jet lag or shift work, there are studies with melatonin (PubMed 29318587). For longer-lasting sleep problems, the European guideline names cognitive behavioural therapy as the first choice (PubMed 28875581). Discuss with your doctor whether a product is suitable for you. Do not stop a prescribed medication without talking to your doctor first.

Cortisol too low in the morning, too high in the evening: what does it mean?

A saliva test sometimes shows a pattern: the morning value is rather low and the evening value rather high. The curve is then flatter than you would expect. This can fit with the feeling of finding it hard to get going in the morning and being unable to switch off in the evening. But a single value is only a snapshot. Cortisol reacts to many things, such as a short night or stress on the day of the test.

The time of day also matters. The morning value in particular depends heavily on exactly when after waking up the sample is taken. Experts stress that the measurement is only meaningful if the schedule is followed closely (PubMed 26563991). This is why values are always interpreted together with your everyday life, sleep and symptoms.

When you should see a doctor

Unusual cortisol values are rarely caused by diseases of the adrenal glands or the pituitary gland. In Cushing's syndrome, the body produces too much cortisol over a long period. The work-up includes, among other things, a saliva test late in the evening; if the result is abnormal, the guideline recommends endocrinological assessment with a second test (PubMed 18334580). In Addison's disease, a form of adrenal insufficiency, the body produces too little cortisol. Here doctors measure ACTH and cortisol in the blood in the morning or carry out a stimulation test (PubMed 26760044).

Both diseases are rare. A single raised or low saliva value does not mean either of these diagnoses. But do talk to a doctor if, for example, unwanted weight gain around the abdomen, a round face and thin skin appear – or severe exhaustion, weight loss and dizziness when standing up. Sleep problems lasting for weeks also belong in a conversation with your doctor.

What you can do yourself

• Use light as a switch: go outside as soon as possible in the morning, and use dim, warm light in the evening.
• Put screens away before sleep or at least turn them down considerably.
• Separate the evening from the day: finish emails and planning before dinner.
• Regular times for getting up, even at the weekend.

If you always wake up at the same time at night, also read Waking up at 3am every night: what cortisol, alcohol and blood sugar have to do with it.

Measuring cortisol and melatonin

Because both hormones follow a daily rhythm, the timing of the measurement is crucial:

• The Cortisol daily profile measures cortisol in saliva in the morning about 30 minutes after waking up, at midday and in the evening, plus DHEA from the morning sample. It shows the course over the day, not a night-time value.
• The Melatonin test measures free melatonin in a saliva sample that you take at 2am in the dark. The amount varies greatly from person to person.
• The Stress & sleep lab package combines both with neurotransmitter tryptophan metabolism and a cell stress profile in morning urine, as well as the Epigenetik Stress Monitor from capillary blood.

The values are building blocks for a conversation, not a diagnosis. The ORY expert team, your doctor or your naturopath can support you in interpreting them.

In brief

• Melatonin rises in the evening when it gets dark; cortisol rises in the early hours of the morning, peaking shortly after waking up.
• Light in the evening and screens slow down melatonin and push the "night" signal later.
• That cortisol directly inhibits melatonin has not been clearly shown. But stress and poor sleep are linked to more cortisol in the evening.
• "Melatonin deficiency" is not an established diagnosis; values are often lower in older age, but not in everyone.
• Individual saliva values are interpreted carefully and together with your everyday life.

Frequently asked questions

Is cortisol the opposite of melatonin?

Over the course of the day, yes: melatonin is high in the evening and at night, cortisol in the morning (PubMed 29318587) (PubMed 23148157). Both follow the same internal clock and therefore run in opposite directions.

Does cortisol block melatonin?

This has not been clearly shown in humans. What is certain is that light slows down melatonin (PubMed 21193540) and that people with chronic insomnia had more cortisol in the evening (PubMed 11502812).

What does high cortisol in the evening mean?

A raised evening value in saliva can fit with stress or poor sleep. But it is a snapshot and is interpreted together with the course over the day and your symptoms. Rarely, a disease such as Cushing's syndrome lies behind it, which is investigated by a doctor with further tests (PubMed 18334580).

What are the symptoms of melatonin deficiency?

Difficulty falling asleep and sleep that keeps shifting later are often mentioned. But these symptoms have many causes. "Melatonin deficiency" is not an established diagnosis.

Can you test for melatonin deficiency?

Melatonin can be measured in saliva, for example in a night-time sample taken in the dark. Because values vary greatly from person to person, the result is interpreted together with your sleep pattern, not as a deficiency diagnosis.

Does melatonin decrease with age?

Often, yes. In one study, the night-time peak was already considerably lower at around 40 (PubMed 12485366). In healthy older people taking no medication, however, another study found no difference (PubMed 10569297).

Sources

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5. Gooley JJ et al. Exposure to room light before bedtime suppresses melatonin onset and shortens melatonin duration in humans. J Clin Endocrinol Metab. 2011. PubMed 21193540
6. Chang AM et al. Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness. PNAS. 2015. PubMed 25535358
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