Sweet Thresholds in Healthy Volunteers Study

Assessing Taste Thresholds and Scores on Standardised Mood Questionnaires in Participants Without Mood Disorders

The sweet threshold (concentration of sucrose in water) at which healthy participants can detect a sweet flavour will be recorded.

The sweet threshold (concentration of sucrose in water) at which healthy participants can detect a sweet flavour will be recorded by means of application on a cotton bud to the anterior third of the tongue. Solutions will be presented in a pseudo-randomised order. Mood questionnaires will be completed (to check that participants are indeed healthy). The questionnaires used will be the Patient Health Questionnaire 9 (PHQ9), Beck's Depression Inventory (BDI) and Generalised Anxiety Disorder Questionnaire 7 (GAD-7).

This data is being collected with the intention of its use for comparison with sweet thresholds established in other populations using the same method of sweet threshold estimation.

Inclusion Criteria:

. Male and female adults of 18 years old and over;

• Participants without a diagnosis of major depressive disorder (MDD) / anxiety disorder;
• Participants not taking an antidepressant during the preceding 6 months
• Not suffering from significant other mental or physical illness, such as confirmed psychosis, end of life care, or any other condition assessed as significant by the Site Investigator;
• Willing and able to comply with all study-related procedures;
• Not having COVID 19 or continuing effects of COVID 19 including altered sense of taste;
• Understands the study requirements and the treatment procedures and is able to provide written informed consent.

Exclusion Criteria:

• Taking antidepressant medication currently or during the previous 6 months;
• Known or suspected hypersensitivity or intolerance to any taste testing solutions, or any of their excipients;
• A history or presence of neurological or confounding psychiatric conditions (such as stroke, traumatic brain injury, epilepsy, space occupying lesions, multiple sclerosis, Parkinson's disease, vascular dementia, transient ischemic attack, or schizophrenia);
• Patients with a diagnosis of chronic pain;
• Pregnancy or possibility pregnancy, or breastfeeding;
• Participants using supplements containing psychoactive herbs (for example St Johns Wort or 5-HTP (5-Hydroxytryptophan, also known as oxitriptan);
• Participants regularly using psychoactive stimulants (for example MDMA);
• Participants unable or unwilling to comply with study procedures.