Flag of the European Union EU Clinical Trials Register Help

Clinical trials

The European Union Clinical Trials Register allows you to search for protocol and results information on:
  • interventional clinical trials that are conducted in the European Union (EU) and the European Economic Area (EEA);
  • clinical trials conducted outside the EU / EEA that are linked to European paediatric-medicine development.
  • Learn   more about the EU Clinical Trials Register   including the source of the information and the legal basis.


    The EU Clinical Trials Register currently displays   42336   clinical trials with a EudraCT protocol, of which   6971   are clinical trials conducted with subjects less than 18 years old.
    The register also displays information on   18700   older paediatric trials (in scope of Article 45 of the Paediatric Regulation (EC) No 1901/2006).


    Phase 1 trials conducted solely in adults and that are not part of an agreed PIP are not public in the EU CTR (refer to European Guidance 2008/C 168/02   Art. 3 par. 2 and   Commission Guideline 2012/C 302/03,   Art. 5) .

    Clinical Trials marked as "Trial now transitioned" were transitioned to the Clinical Trial Regulation 536/2014 and can be further followed in the Clinical Trial Information System  
     
    Examples: Cancer AND drug name. Pneumonia AND sponsor name.
    How to search [pdf]
    Search Tips: Under advanced search you can use filters for Country, Age Group, Gender, Trial Phase, Trial Status, Date Range, Rare Diseases and Orphan Designation. For these items you should use the filters and not add them to your search terms in the text field.
    Advanced Search: Search tools
     

    < Back to search results

    Download PDF

    Clinical Trial Results:
    The effect of dopamine on reading motivation and achievement.

    Summary
    EudraCT number
    2014-001352-36
    Trial protocol
    NL  
    Global end of trial date
    17 Jul 2017

    Results information
    Results version number
    v1(current)
    This version publication date
    14 Jan 2022
    First version publication date
    14 Jan 2022
    Other versions
    Summary report(s)
    Swart & Sikkema-de Jong (2021) - Current Psychology

    Trial information

    Close Top of page
    Trial identification
    Sponsor protocol code
    DOPAREAD1
    Additional study identifiers
    ISRCTN number
    -
    US NCT number
    -
    WHO universal trial number (UTN)
    -
    Sponsors
    Sponsor organisation name
    Leiden University
    Sponsor organisation address
    Wassenaarseweg 52, Leiden, Netherlands, 2333AK
    Public contact
    Dr. E.K. Swart, Leiden University, e.k.swart@fsw.leidenuniv.nl
    Scientific contact
    Dr. E.K. Swart, Leiden University, e.k.swart@fsw.leidenuniv.nl
    Paediatric regulatory details
    Is trial part of an agreed paediatric investigation plan (PIP)
    No
    Does article 45 of REGULATION (EC) No 1901/2006 apply to this trial?
    No
    Does article 46 of REGULATION (EC) No 1901/2006 apply to this trial?
    No
    Results analysis stage
    Analysis stage
    Final
    Date of interim/final analysis
    11 Dec 2018
    Is this the analysis of the primary completion data?
    Yes
    Primary completion date
    17 Jul 2017
    Global end of trial reached?
    Yes
    Global end of trial date
    17 Jul 2017
    Was the trial ended prematurely?
    No
    General information about the trial
    Main objective of the trial
    The main goal of the study is to investigate if small amounts of dopamine could influence engagement during reading, comprehension of the story and vocabulary learning and to investigate if the effect of dopamine is different for carriers of the long or short variant of the DRD4 gene. Additionally, the effect of dopamine on how participants value reading is investigated.
    Protection of trial subjects
    Students with dyslexia, medical illnesses indicating a risk in using haloperidol (e.g. cardiac illness, depression, thyroid disorders, or glaucoma), or known drug allergies were excluded from participation in the study. Also students were excluded if they were using medication (other than contraceptives) or drugs in the two weeks prior to the experiment or if they were pregnant or lactating during the experiment. During study sessions participants were constantly accompanied by a researcher. Participants were informed beforehand that side-effects of the one-time administration of the drug were unlikely to occur, but that they should tell the researcher immediately if they thought they would possibly suffer from side-effects.
    Background therapy
    -
    Evidence for comparator
    -
    Actual start date of recruitment
    01 Nov 2014
    Long term follow-up planned
    No
    Independent data monitoring committee (IDMC) involvement?
    No
    Population of trial subjects
    Number of subjects enrolled per country
    Country: Number of subjects enrolled
    Netherlands: 80
    Worldwide total number of subjects
    80
    EEA total number of subjects
    80
    Number of subjects enrolled per age group
    In utero
    0
    Preterm newborn - gestational age < 37 wk
    0
    Newborns (0-27 days)
    0
    Infants and toddlers (28 days-23 months)
    0
    Children (2-11 years)
    0
    Adolescents (12-17 years)
    0
    Adults (18-64 years)
    80
    From 65 to 84 years
    0
    85 years and over
    0

    Subject disposition

    Close Top of page
    Recruitment
    Recruitment details
    A total number of 200 undergraduate students from universities in the Netherlands signed up for participation in our study. After genotyping, 80 students (40 carriers of the DRD4-7r allele, and 40 participants who did not) were selected to participate in the experimental sessions. Recruitment took place between in 2015 and 2016.

    Pre-assignment
    Screening details
    Inclusion criteria: Women, 18 years or older, right-handed. Exclusion criteria: Dyslexia, medical illnesses indicating a risk in using haloperidol (e.g. cardiac illness, depression, thyroid disorders, or glaucoma), known drug allergies, using medication or drugs in the two weeks prior, pregnancy or lactating during the experiment

    Period 1
    Period 1 title
    Experimental sessions (overall period)
    Is this the baseline period?
    Yes
    Allocation method
    Randomised - controlled
    Blinding used
    Double blind
    Roles blinded
    Subject, Investigator
    Blinding implementation details
    To ensure that the study design was double-blind, randomization of the order of treatments (Sinemet125 or placebo) and the order of texts that were read in both experimental sessions (text A and text B) was carried out by the university hospital pharmacy, resulting in four different combinations of the order of treatment condition and text.

    Arms
    Are arms mutually exclusive
    No

    Arm title
    Dopamine-condition
    Arm description
    The study had a randomized, double-blind placebo-controlled within-subjects experimental design. A total of 80 participants were submitted to both experimental conditions (dopamine and placebo) at two separate lab sessions.
    Arm type
    Experimental

    Investigational medicinal product name
    SINEMET 125
    Investigational medicinal product code
    RVG 08740
    Other name
    Pharmaceutical forms
    Capsule
    Routes of administration
    Oral use
    Dosage and administration details
    At the beginning of the lab sessions, participants received capsules containing Sinemet125 and took the capsules orally.

    Arm title
    Placebo-condition
    Arm description
    A total of 80 participants were submitted to both experimental conditions (dopamine and placebo) at two separate lab sessions.
    Arm type
    Placebo

    Investigational medicinal product name
    Placebo
    Investigational medicinal product code
    Other name
    Pharmaceutical forms
    Capsule
    Routes of administration
    Oral use
    Dosage and administration details
    Lactose monohydrate with 1 % magnesium stearate (125mg)

    Number of subjects in period 1
    Dopamine-condition Placebo-condition
    Started
    80
    80
    Completed
    80
    80

    Baseline characteristics

    Close Top of page
    Baseline characteristics reporting groups
    Reporting group title
    Experimental sessions
    Reporting group description
    80 students (mean age 21.38 years, SD = 1,84; 40 participants carrying the DRD4-7R allele, and 40 participants who did not) were selected to participate in the experimental sessions (both the dopamine and placebo condition). Students in the two groups (DRD4-7R+ and DRD4-7R-) did not differ in age, reading motivation, language skills, executive functioning in daily life, attentional control in daily life, or baseline reading speed.

    Reporting group values
    Experimental sessions Total
    Number of subjects
    80 80
    Age categorical
    Units: Subjects
        Adults (18+)
    80 80
    Age continuous
    Units: years
        arithmetic mean (standard deviation)
    21.38 ± 1.84 -
    Gender categorical
    Units: Subjects
        Female
    80 80
        Male
    0 0
    Reading motivation
    Participants completed a researcher-constructed reading motivation survey. The survey consisted of three subscales: engagement in reading related activities, attitude towards reading for pleasure, and reading in spare time. Higher scores reflected higher reading motivation.
    Units: 0.1
        arithmetic mean (standard deviation)
    0.00 ± 1.00 -
    Language skills
    Participants completed a researcher-constructed language test, containing of four subtests: spelling, grammar, vocabulary and syntax.
    Units: 0.1
        arithmetic mean (standard deviation)
    0.00 ± 1.00 -
    Executive functioning
    Participants completed the Behavior Rating Inventory of Executive Function—Adult version (BRIEFA; Scholte & Noens, 2011), a self-report questionnaire of 75 items designed to examine adult’s executive functions in daily life.
    Units: 1.0
        arithmetic mean (standard deviation)
    102.91 ± 20.33 -
    Attentional Control
    Participants completed a Dutch translation of the Attentional Control Scale (ACS; Derryberry & Reed, 2002).
    Units: 1.0
        arithmetic mean (standard deviation)
    53.55 ± 8.51 -
    Subject analysis sets

    Subject analysis set title
    DRD4 7R+
    Subject analysis set type
    Sub-group analysis
    Subject analysis set description
    The final sample consisted of 40 students with the DRD4 7R+ genotype and 40 students with the DRD4 7R- genotype.

    Subject analysis set title
    DRD4 7R-
    Subject analysis set type
    Sub-group analysis
    Subject analysis set description
    The final sample consisted of 40 students with the DRD4 7R+ genotype and 40 students with the DRD4 7R- genotype.

    Subject analysis sets values
    DRD4 7R+ DRD4 7R-
    Number of subjects
    40
    40
    Age categorical
    Units: Subjects
        Adults (18+)
    40
    40
    Age continuous
    Units: years
        arithmetic mean (standard deviation)
    21.18 ± 1.65
    21.58 ± 2.01
    Gender categorical
    Units: Subjects
        Female
    40
    40
        Male
    0
    0
    Reading motivation
    Participants completed a researcher-constructed reading motivation survey. The survey consisted of three subscales: engagement in reading related activities, attitude towards reading for pleasure, and reading in spare time. Higher scores reflected higher reading motivation.
    Units: 0.1
        arithmetic mean (standard deviation)
    0.11 ± 0.95
    -0.11 ± 1.05
    Language skills
    Participants completed a researcher-constructed language test, containing of four subtests: spelling, grammar, vocabulary and syntax.
    Units: 0.1
        arithmetic mean (standard deviation)
    0.03 ± 1.08
    -0.03 ± 0.92
    Executive functioning
    Participants completed the Behavior Rating Inventory of Executive Function—Adult version (BRIEFA; Scholte & Noens, 2011), a self-report questionnaire of 75 items designed to examine adult’s executive functions in daily life.
    Units: 1.0
        arithmetic mean (standard deviation)
    102.00 ± 20.82
    103.82 ± 19.83
    Attentional Control
    Participants completed a Dutch translation of the Attentional Control Scale (ACS; Derryberry & Reed, 2002).
    Units: 1.0
        arithmetic mean (standard deviation)
    53.80 ± 8.00
    53.30 ± 9.01

    End points

    Close Top of page
    End points reporting groups
    Reporting group title
    Dopamine-condition
    Reporting group description
    The study had a randomized, double-blind placebo-controlled within-subjects experimental design. A total of 80 participants were submitted to both experimental conditions (dopamine and placebo) at two separate lab sessions.

    Reporting group title
    Placebo-condition
    Reporting group description
    A total of 80 participants were submitted to both experimental conditions (dopamine and placebo) at two separate lab sessions.

    Subject analysis set title
    DRD4 7R+
    Subject analysis set type
    Sub-group analysis
    Subject analysis set description
    The final sample consisted of 40 students with the DRD4 7R+ genotype and 40 students with the DRD4 7R- genotype.

    Subject analysis set title
    DRD4 7R-
    Subject analysis set type
    Sub-group analysis
    Subject analysis set description
    The final sample consisted of 40 students with the DRD4 7R+ genotype and 40 students with the DRD4 7R- genotype.

    Primary: Attentional control - average frontal TBR

    Close Top of page
    End point title
    Attentional control - average frontal TBR [1]
    End point description
    End point type
    Primary
    End point timeframe
    during reading
    Notes
    [1] - No statistical analyses have been specified for this primary end point. It is expected there is at least one statistical analysis for each primary end point.
    Justification: A repeated measures ANOVA with condition (dopamine vs. placebo) and type of attentional control measure (frontal TBR during reading, SD in frontal TBR during reading and self-reports of attentional control during reading) as within-subjects factors showed no main effect of condition (F(1,75) = 1.48, p = 0.23). Attentional control during reading did not differ between the levodopa condition and the placebo condition.
    End point values
    Dopamine-condition Placebo-condition
    Number of subjects analysed
    79
    80
    Units: 0.01
        arithmetic mean (standard deviation)
    .40 ± .20
    .39 ± .17
    No statistical analyses for this end point

    Primary: Attentional control - SD in frontal TBR

    Close Top of page
    End point title
    Attentional control - SD in frontal TBR [2]
    End point description
    End point type
    Primary
    End point timeframe
    during reading
    Notes
    [2] - No statistical analyses have been specified for this primary end point. It is expected there is at least one statistical analysis for each primary end point.
    Justification: A repeated measures ANOVA with condition (dopamine vs. placebo) and type of attentional control measure (frontal TBR during reading, SD in frontal TBR during reading and self-reports of attentional control during reading) as within-subjects factors showed no main effect of condition (F(1,75) = 1.48, p = 0.23). Attentional control during reading did not differ between the levodopa condition and the placebo condition.
    End point values
    Dopamine-condition Placebo-condition
    Number of subjects analysed
    78
    79
    Units: 0.01
        arithmetic mean (standard deviation)
    .09 ± .06
    .09 ± .05
    No statistical analyses for this end point

    Primary: Attentional control - self-reports

    Close Top of page
    End point title
    Attentional control - self-reports [3]
    End point description
    End point type
    Primary
    End point timeframe
    during reading
    Notes
    [3] - No statistical analyses have been specified for this primary end point. It is expected there is at least one statistical analysis for each primary end point.
    Justification: A repeated measures ANOVA with condition (dopamine vs. placebo) and type of attentional control measure (frontal TBR during reading, SD in frontal TBR during reading and self-reports of attentional control during reading) as within-subjects factors showed no main effect of condition (F(1,75) = 1.48, p = 0.23). Attentional control during reading did not differ between the levodopa condition and the placebo condition.
    End point values
    Dopamine-condition Placebo-condition
    Number of subjects analysed
    79
    79
    Units: 1.00
        arithmetic mean (standard deviation)
    3.09 ± 2.47
    2.97 ± 2.76
    No statistical analyses for this end point

    Primary: Summary task

    Close Top of page
    End point title
    Summary task [4]
    End point description
    End point type
    Primary
    End point timeframe
    post-test
    Notes
    [4] - No statistical analyses have been specified for this primary end point. It is expected there is at least one statistical analysis for each primary end point.
    Justification: A repeated measures ANOVA was performed with condition (dopamine vs. placebo) and type of reading comprehension measure (summary task, text-level comprehension questions, spelling questions, open word meaning questions, and MC word meaning questions) as within-subjects factors. There was a significant main effect of condition on reading comprehension (F(1,79) = 11.55, p = 0.001). Participants performed worse on reading comprehension in the levodopa condition than in the placebo condition.
    End point values
    Dopamine-condition Placebo-condition
    Number of subjects analysed
    80
    80
    Units: 1.00
        arithmetic mean (standard deviation)
    24.70 ± 13.61
    25.47 ± 13.14
    No statistical analyses for this end point

    Primary: Text-level comprehension questions

    Close Top of page
    End point title
    Text-level comprehension questions [5]
    End point description
    End point type
    Primary
    End point timeframe
    post-test
    Notes
    [5] - No statistical analyses have been specified for this primary end point. It is expected there is at least one statistical analysis for each primary end point.
    Justification: A repeated measures ANOVA was performed with condition (dopamine vs. placebo) and type of reading comprehension measure (summary task, text-level comprehension questions, spelling questions, open word meaning questions, and MC word meaning questions) as within-subjects factors. There was a significant main effect of condition on reading comprehension (F(1,79) = 11.55, p = 0.001). Participants performed worse on reading comprehension in the levodopa condition than in the placebo condition.
    End point values
    Dopamine-condition Placebo-condition
    Number of subjects analysed
    80
    80
    Units: 0.1
        arithmetic mean (standard deviation)
    31.82 ± 17.63
    36.72 ± 17.61
    No statistical analyses for this end point

    Primary: MC word meaning questions

    Close Top of page
    End point title
    MC word meaning questions [6]
    End point description
    End point type
    Primary
    End point timeframe
    post-test
    Notes
    [6] - No statistical analyses have been specified for this primary end point. It is expected there is at least one statistical analysis for each primary end point.
    Justification: A repeated measures ANOVA was performed with condition (dopamine vs. placebo) and type of reading comprehension measure (summary task, text-level comprehension questions, spelling questions, open word meaning questions, and MC word meaning questions) as within-subjects factors. There was a significant main effect of condition on reading comprehension (F(1,79) = 11.55, p = 0.001). Participants performed worse on reading comprehension in the levodopa condition than in the placebo condition.
    End point values
    Dopamine-condition Placebo-condition
    Number of subjects analysed
    80
    80
    Units: 1.00
        arithmetic mean (standard deviation)
    44.00 ± 9.42
    46.88 ± 13.56
    No statistical analyses for this end point

    Primary: Open word meaning questions

    Close Top of page
    End point title
    Open word meaning questions [7]
    End point description
    End point type
    Primary
    End point timeframe
    post-test
    Notes
    [7] - No statistical analyses have been specified for this primary end point. It is expected there is at least one statistical analysis for each primary end point.
    Justification: A repeated measures ANOVA was performed with condition (dopamine vs. placebo) and type of reading comprehension measure (summary task, text-level comprehension questions, spelling questions, open word meaning questions, and MC word meaning questions) as within-subjects factors. There was a significant main effect of condition on reading comprehension (F(1,79) = 11.55, p = 0.001). Participants performed worse on reading comprehension in the levodopa condition than in the placebo condition.
    End point values
    Dopamine-condition Placebo-condition
    Number of subjects analysed
    80
    80
    Units: 1.00
        arithmetic mean (standard deviation)
    4.79 ± 5.66
    6.42 ± 7.21
    No statistical analyses for this end point

    Primary: Spelling questions

    Close Top of page
    End point title
    Spelling questions [8]
    End point description
    End point type
    Primary
    End point timeframe
    post-test
    Notes
    [8] - No statistical analyses have been specified for this primary end point. It is expected there is at least one statistical analysis for each primary end point.
    Justification: A repeated measures ANOVA was performed with condition (dopamine vs. placebo) and type of reading comprehension measure (summary task, text-level comprehension questions, spelling questions, open word meaning questions, and MC word meaning questions) as within-subjects factors. There was a significant main effect of condition on reading comprehension (F(1,79) = 11.55, p = 0.001). Participants performed worse on reading comprehension in the levodopa condition than in the placebo condition.
    End point values
    Dopamine-condition Placebo-condition
    Number of subjects analysed
    80
    80
    Units: 1.00
        arithmetic mean (standard deviation)
    8.33 ± 5.76
    10.50 ± 7.89
    No statistical analyses for this end point

    Adverse events

    Close Top of page
    Adverse events information
    Timeframe for reporting adverse events
    Experimental sessions
    Adverse event reporting additional description
    None of the participants suffered from serious adverse events during or after our study related to the intake of Sinemet125 or the placebo treatment. Except for one participant reporting nausea in the placebo condition, no side effects of the medication were reported by the participants.
    Assessment type
    Non-systematic
    Dictionary used for adverse event reporting
    Dictionary name
    N.A.
    Dictionary version
    N.A.
    Reporting groups
    Reporting group title
    Dopamine condition
    Reporting group description
    -

    Reporting group title
    Placebo condition
    Reporting group description
    -

    Serious adverse events
    Dopamine condition Placebo condition
    Total subjects affected by serious adverse events
         subjects affected / exposed
    0 / 80 (0.00%)
    0 / 80 (0.00%)
         number of deaths (all causes)
    0
    0
         number of deaths resulting from adverse events
    0
    0
    Frequency threshold for reporting non-serious adverse events: 1%
    Non-serious adverse events
    Dopamine condition Placebo condition
    Total subjects affected by non serious adverse events
         subjects affected / exposed
    0 / 80 (0.00%)
    1 / 80 (1.25%)
    Injury, poisoning and procedural complications
    Nausea
         subjects affected / exposed
    0 / 80 (0.00%)
    1 / 80 (1.25%)
         occurrences all number
    0
    1

    More information

    Close Top of page

    Substantial protocol amendments (globally)

    Were there any global substantial amendments to the protocol? No

    Interruptions (globally)

    Were there any global interruptions to the trial? No

    Limitations and caveats

    Limitations of the trial such as small numbers of subjects analysed or technical problems leading to unreliable data.
    N.A.
    For support, visit the EMA Service Desk , log in using your EMA account and open a ticket specifying "EU CTR" in your request.
    If you do not have an account, please visit the EMA Account management page page click on "Create an EMA account" and follow the instructions.
    The status of studies in GB is no longer updated from 1.1.2021
    For the UK, as from 1.1.2021, EU Law applies only to the territory of Northern Ireland (NI) to the extent foreseen in the Protocol on Ireland/NI
    EU Clinical Trials Register Service Desk: https://servicedesk.ema.europa.eu
    European Medicines Agency © 1995-2022 | Domenico Scarlattilaan 6, 1083 HS Amsterdam, The Netherlands
    Legal notice
    EMA HMA