Sweet Thresholds in Healthy Volunteers Study

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.