Investigating the effects of acute tryptophan loading on attention and impulsivity in adults with and without Attention Deficit Hyperactivity Disorder (ADHD)
| ISRCTN | ISRCTN15119603 |
|---|---|
| DOI | https://doi.org/10.1186/ISRCTN15119603 |
- Submission date
- 27/04/2023
- Registration date
- 03/05/2023
- Last edited
- 12/12/2023
- Recruitment status
- No longer recruiting
- Overall study status
- Completed
- Condition category
- Mental and Behavioural Disorders
Plain English summary of protocol
Background and study aims
ADHD is a condition where people have trouble paying attention, are impulsive, and hyperactive. It's not just a childhood thing - some adults have it too. The most common treatment is medicine that helps with the chemicals in the brain that affect attention, but this medicine can have bad side effects. Some research suggests that other chemicals in the brain, like serotonin, might be involved in ADHD too. Serotonin can be affected by what we eat, especially by a chemical called tryptophan. There haven't been many studies on using tryptophan to treat ADHD in adults, and the ones that have been done haven't looked at the main ADHD symptoms. This study wants to see if increasing tryptophan levels can help with attention and impulsivity in both healthy people and those with ADHD. They will compare how people do on cognitive tasks after taking tryptophan supplements to how they do after taking a control supplement with a normal amount of tryptophan.
Who can participate?
Adults aged 18-35 years with:
1. No current or previous diagnosis of ADHD
2. A current diagnosis of ADHD but not currently receiving any drug treatment for the condition (and have not done so for 3 months)
3. A current diagnosis of ADHD and currently receiving and adhering to medication treatment for the condition with at least 70% adherence
What does the study involve?
Participants will first complete a brief online screening survey (<10 minutes) to assess eligibility to participate. Eligible participants will be asked to provide a UK post address for a protein powder to be sent and will be invited to an online test session. Testing will be in two phases – before and after consuming the protein shake – with the same computerised tests completed in both phases and aim to measure attention and impulsivity. Brief descriptions of the tests are given below:
1. Test of attention – participants will be asked to press a letter on a keyboard to respond to a target stimulus whilst inhibiting responses to non-target stimulus. This will provide a measure of attention and motor impulsivity
2. Tests of impulsivity – two specific tests will be used to measure impulsivity. In the first test participants will be asked to make choices, using keyboard presses, between hypothetical rewards now or at a point in the future for several different delays e.g. 1 week, 2 weeks, 1 month, 3 months, 6 months and 1 year. In the second test, participants will be shown four decks of cards (labelled A, B, C, and D) and asked to choose 100 times from the decks with two decks giving greater gains and losses. These tests measure cognitive and temporal impulsivity
What are the possible benefits and risks of participating?
The data collected will provide valuable information about the effectiveness of tryptophan in treating ADHD and therefore has the potential to be beneficial to patients with the condition in the future. There are no direct benefits to participants for participating in this study, although those who attend and complete testing will receive an Amazon voucher as a ‘thank you’. The researchers don’t anticipate any specific risks in taking part in the study because we will only enroll participants who can safely consume the protein shake (e.g. do not have allergies to any of the ingredients). We will be asking about symptoms of ADHD and use of medication, where appropriate. These questions are asked during the screening survey and it is clear this information is required in the information sheet so it is hoped that participants choosing to participate in the study will be comfortable sharing this information. If they do not, they can withdraw at any point.
Where is the study run from?
The researchers conducting this study are based at King's College London (UK) but the study is an online study so testing can be done from anywhere and uses MS Teams.
When is the study starting and how long is it expected to run for?
May 2020 to September 2023
Who is funding the study?
Investigator initiated and funded
Who is the main contact?
Dr Eleanor Dommett, eleanor.dommett@kcl.ac.uk
Contact information
Principal Investigator
Dept of Psychology
Rm 2.13 Addison House
Guy's Campus
King's College London
London
SE1 1UL
United Kingdom
 ORCID ID |
0000-0002-6973-8762 |
|---|---|
| Phone | +44 2078486928 |
| eleanor.dommett@kcl.ac.uk |
Study information
| Study design | Interventional double blind randomized controlled trial |
|---|---|
| Primary study design | Interventional |
| Secondary study design | Randomised controlled trial |
| Study setting(s) | Home |
| Study type | Treatment |
| Participant information sheet | 43566 PIS V3 07.10.21.pdf |
| Scientific title | Investigating the effects of tryptophan modulation on attention and impulsivity in adults with and without Attention Deficit Hyperactivity Disorder: A double blind randomised controlled trial |
| Study acronym | TrypCoreADHD |
| Study objectives | 1. Participants with ADHD will perform significantly worse on tasks measuring attention and impulsivity in comparison to those without ADHD prior to any tryptophan modulation. 2. There will be a dose-dependent effect of tryptophan modulation on attention and impulsivity that will differ between those with ADHD and those without. |
| Ethics approval(s) |
Approved 15/05/2020, King's College London PNM Research Ethics Subcommittee (5.9 Waterloo Bridge Wing, Waterloo Road, London, SE1 9NH, United Kingdom; +44 (0)207 8484020; rec@kcl.ac.uk), ref: 19/20-17983 |
| Health condition(s) or problem(s) studied | Attention Deficit Hyperactivity Disorder (ADHD) |
| Intervention | Participants will first complete a brief online screening survey (<10 minutes). This information is used to assess eligibility and allocate participants to specific groups (e.g. those with and without ADHD). The survey assesses: - Information relating to food intolerance and diet - Demographic information e.g., age and gender - Clinical information including use of medication, ADHD symptoms Finally, participants will be asked to provide an email address so that they can be contacted by the research team to confirm eligibility and book in a test session where appropriate. A protein powder sachet will be sent to the participants at a UK address in advance of this session. Test sessions take place online via MS Teams. On arrival in the online space, participants will be directed to make up their protein shake from the posted powder and then refrigerate this. They will be asked to complete three computerised tests via their browser. They will be asked to have their camera on and screen share throughout. Brief descriptions of the tests are given below: 1. Test of variables of attention (TOVA) task – participants will be asked to press a letter on a keyboard to respond to a target stimulus whilst inhibiting responses to non-target stimulus. This will provide a measure of attention and motor impulsivity. 2. Delayed Discounting Task (DDT) - participants will be asked to make choices, using keyboard presses, between hypothetical rewards now or at a point in the future for several different delays e.g. 1 week, 2 weeks, 1 month, 3 months, 6 months and 1 year. This provides a measure of temporal impulsivity. 3. Iowa Gambling Task - participants will be shown 4 decks of cards (labelled A, B, C, and D) and asked to choose 100 times from the decks with two decks giving greater gains and losses. This provides a measures of cognitive impulsivity. After completion of these tasks participants will have around 10 mins to consume the protein shake before taking a 1 hour break and then returning to the online call. On return the tasks will be repeated. The protein shake will either contain a balanced amino acid profile, a low loading of tryptophan or a high loading of tryptophan. The participants and researcher running the session will not be aware of which type of protein shake is being consumed to avoid any bias. We are using stratified randomisation (stratified by gender and medication use) with a random number generator to allocate to intervention condition. |
| Intervention type | Supplement |
| Primary outcome measure | Measured pre and post intervention (baseline and ~1 hour): 1. Attention measured using the computerised Test of Variable of Attention (TOVA) task (omission errors, response sensitivity, reaction time). 2. Motor impulsivity measured using the computerised Test of Variable of Attention (TOVA) task (commission errors). 3. Temporal impulsivity measured using the computerised Delay Discounting Task (indifference points, discounting function, area under the curve). 4. Cognitive impulsivity measured using the computerised Iowa Gambling Task (proportion of risky decisions, net score). |
| Secondary outcome measures | There are no secondary outcome measures |
| Overall study start date | 01/05/2020 |
| Completion date | 30/09/2023 |
Eligibility
| Participant type(s) | Mixed |
|---|---|
| Age group | Adult |
| Lower age limit | 18 Years |
| Upper age limit | 35 Years |
| Sex | Both |
| Target number of participants | 144 |
| Total final enrolment | 144 |
| Key inclusion criteria | All participants: 1. Adults aged 18-35 years Healthy control participants (HC): 2. No diagnosis of ADHD and score on the Adult ADHD Self-Report Scale below the threshold indicative of ADHD. ADHD 3. Existing current diagnosis of ADHD and score on the Adult ADHD Self-Report Scale above the threshold indicative of ADHD. 4. Either not receiving ADHD medication and have not received any for a period of at least 3 months or receiving medication for ADHD (psychostimulant or non-stimulant) and adhering to this with a rate of at least 70%. |
| Key exclusion criteria | 1. Gluten or lactose intolerance, as participants will be asked to ingest a whey protein drink 2. Current or past diagnosis of nutritional, psychiatric (excluding ADHD) or neurological illnesses 3. Being pregnant/breastfeeding 4. Being a smoker (including e-cigarettes) 5. Currently taking medication known to affect the serotonergic system such as antidepressants 6. Learning disabilities 7. Following a restrictive diet (e.g. keto), as this might interfere with the experiment |
| Date of first enrolment | 01/07/2020 |
| Date of final enrolment | 01/08/2023 |
Locations
Countries of recruitment
- England
- United Kingdom
Study participating centre
London
SE1 1UL
United Kingdom
Sponsor information
University/education
57 Waterloo Road
Room 5.31
James Clerk Maxwell Building
London
SE1 8WA
England
United Kingdom
| Phone | +44 (0)207 8483224 |
|---|---|
| reza.razavi@kcl.ac.uk | |
| Website | http://www.kcl.ac.uk/index.aspx |
"ROR" |
https://ror.org/0220mzb33 |
Funders
Funder type
Other
No information available
Results and Publications
| Intention to publish date | 01/01/2024 |
|---|---|
| Individual participant data (IPD) Intention to share | Yes |
| IPD sharing plan summary | Stored in publicly available repository, Available on request |
| Publication and dissemination plan | We plan to publish the results in a open access peer reviewed scientific journal. We will also make the key information available via our social media. |
| IPD sharing plan | The datasets generated during and/or analysed during the current study are/will be available upon request from the principal investigator (Dr Eleanor Dommett, eleanor.dommett@kcl.ac.uk). |
Study outputs
| Output type | Details | Date created | Date added | Peer reviewed? | Patient-facing? |
|---|---|---|---|---|---|
| Participant information sheet | version 3 | 07/10/2021 | 03/05/2023 | No | Yes |
| Protocol file | 17/08/2023 | No | No | ||
| Results article | 30/11/2023 | 05/12/2023 | Yes | No | |
| Dataset | 14/10/2023 | 12/12/2023 | No | No |
Additional files
Editorial Notes
12/12/2023: A dataset was added and the participant level data sharing statement was updated.
05/12/2023: Publication reference added.
17/08/2023: Protocol and total final enrolment added.
03/05/2023: Trial's existence confirmed by King's College London.
