RecruitingNAINTERVENTIONAL

The Effect of 5-hydroxytryptophan on ADHD Traits and Eye Movements

This research is investigating if a natural supplement, 5-hydroxytryptophan (5-HTP), can help people who find it hard to focus, particularly those with ADHD-like traits. 5-HTP is something your body makes naturally and is linked to serotonin, a brain chemical important for attention. Some theories suggest lower serotonin might be connected to distractibility. Participants will complete surveys and then visit the University of Sheffield. During the visit, they'll do computer tasks that measure eye movements, take either 5-HTP or a dummy pill, wait, and then repeat the tasks. The aim is to see if 5-HTP could be a useful support for attention difficulties.

At a glance

Status

Recruiting

Phase

Sponsor

University of Sheffield

Enrolment target

150

Start

25 Nov 2025

Estimated completion

01 Jun 2027

Attention Deficit and Hyperactivity Disorder (ADHD)Attention Deficit Hyperactivity Disorder in Adults Attention Deficits

What is this study about?

This research is trying to understand if a natural food supplement called 5-hydroxytryptophan, or 5-HTP for short, could help people who struggle with attention, similar to traits seen in ADHD. Our bodies naturally produce 5-HTP from foods we eat, and it plays a key role in making serotonin. Serotonin is an important chemical in the brain that helps control things like sleep, mood, and how well we can pay attention. Some scientists believe that lower levels of serotonin in the brain might make it harder for people to focus and easier for them to get distracted.

Previous studies have looked at serotonin and 5-HTP, and there's an idea that boosting 5-HTP might help improve attention. This study builds on earlier work, trying to get a clearer picture. The researchers want to see if giving people 5-HTP actually changes how easily they get distracted. This information will help them decide if 5-HTP could be a good option to explore further as a potential support for people with attention problems.

It's important to remember that this is a research study to learn more about 5-HTP. It's not about providing a treatment, but gathering information to see if it’s worth more investigation for attention issues.

Key takeaways

This study is looking at a natural supplement (5-HTP) and its effect on attention.
It's for adults aged 18-65 who might have attention difficulties.
You'll complete surveys and one in-person visit to the University of Sheffield.
The visit involves computer tasks, taking 5-HTP or a dummy pill, and repeating tasks.
The aim is to understand if 5-HTP could help with distractibility.
You can withdraw from the study at any time.

Who may be eligible?

To take part in this study, you need to be an adult between 18 and 65 years old. You should have normal vision, or wear glasses or contact lenses to correct your vision so it's normal. The researchers are particularly interested in people who show some signs of ADHD, or do not show signs, based on a short questionnaire you'll complete at the start.

There are some reasons why you wouldn't be able to join. For example, if you're currently taking medication for ADHD or other medicines that affect your brain's serotonin levels (like some antidepressants), you won't be able to participate. Also, if you smoke or vape, are pregnant or breastfeeding, or have certain dietary needs like being vegan or lactose intolerant, you wouldn't be eligible. People with dyslexia are also not included in this particular study.

Could this study suit you?

Answer these quick questions to see if you may be eligible. This is a guide only — the research team makes the final call.

Are you between 18 and 65 years old?
Do you have normal vision (with glasses/contacts if needed)?
Are you currently NOT taking ADHD medication or medicines that affect serotonin (e.g., some antidepressants)?
Are you NOT pregnant, breastfeeding, smoking, or vaping?
Are you NOT vegan, lactose intolerant, or have dyslexia?
Are you able to travel to the University of Sheffield for a single visit?

Answer every question to see your result.

What does participation involve?

If you decide to take part, the first step is to fill out a short online survey about your mental health and everyday behaviours. If your answers show you might be suitable for the study, you'll be invited to an in-person session at the University of Sheffield.

This in-person visit will involve doing some computer tasks that look at how your eyes move and how you pay attention. You'll then be given either a 5-HTP supplement (200mg or 300mg) or a 'dummy' tablet that looks the same but has no active ingredients. You won't know which one you're taking. After taking the tablet, you'll have a 90-minute wait, during which you might relax or do other light activities. Following this wait, you'll repeat the same computer tasks. The total duration of your involvement will be one in-person session, likely lasting a few hours.

Potential risks and benefits

You might not personally benefit from taking part in this study, as the main goal is to gain more knowledge about 5-HTP. However, your involvement could help researchers understand more about attention problems and whether 5-HTP might be a useful aid in the future. As with any supplement, there's a small chance of side effects, although 5-HTP is generally well-tolerated. The researchers will explain any known risks to you. You are free to withdraw from the study at any time, for any reason, without it affecting your medical care or your relationship with the researchers.

Locations (1)

University of Sheffield
Verified postcode
Sheffield, United Kingdom· Recruiting

Common questions

What is 5-HTP?

5-HTP is a natural substance your body makes from food, and it helps create serotonin, a brain chemical important for mood, sleep, and attention.

What is a 'placebo'?

A placebo is a 'dummy' pill that looks just like the real supplement but contains no active ingredients. It helps researchers see if any changes are due to the supplement itself or other factors.

Will I know if I'm taking 5-HTP or the placebo?

No, you won't know which one you're taking. This is called 'blinding' and helps make the study results more accurate.

What are 'eye movements' being studied?

The researchers will use special equipment to track how your eyes move when you're doing attention tasks. This can give clues about how well you're focusing.

Do I have to pay to take part?

No, taking part in research studies is always free.

How to find out more

Eleanor F Jackson

efjackson1@sheffield.ac.uk +447908873415 Official trial record

Always speak to your GP or specialist before deciding to take part in a study.