Unexplained Chronic Cough

This study is testing new ways to help people who have chronic cough that has not improved with typical treatments. One approach is called behavioral cough suppression (BCS) therapy, which teaches people techniques to stop themselves from coughing. Another approach uses a natural substance thought to help reduce the body's sensitivity to cough triggers. In this study, we will test two treatments and include one no-treatment control group. The control group will undergo baseline testing, cough monitoring, and an fMRI brain scan and will be offered BCS at end of study participation. The two treatments include: * BCS therapy with active inhaled treatment (BCS+active), * BCS therapy with inactive inhaled treatment (BCS+inactive), The investigators will enroll 135 adults with refractory chronic cough (RCC). 100 participants who qualify and are willing and able to complete 14 study visits in the clinic and two online study visits will be randomly assigned to one of the two treatments. The no-treatment control group (n=35) will be recruited from adults with RCC who are willing to complete baseline testing and fMRI but are not able or willing to attend 14 study clinic visits. These participants will not be randomized. The investigators want to find out how these treatments affect: * How sensitive someone is to things that make them cough, * How well they can hold back a cough when they try, * How their brain responds to things that cause an urge-to-cough, * And how much their coughing affects their quality of life. The investigators believe both treatments will reduce sensitivity to cough stimulants, reduce cough severity, and improve quality of life, but BCS+active inhaled treatment will work better than BCS+inactive inhaled treatment.

The FORTITUDE trial will provide head-to-head evidence on the benefits and harms of two commonly prescribed neuromodulators (low-dose morphine and pregabalin), the effectiveness of a virtual cough control therapy, exploratory assessment of potential synergy in combining these interventions, and the long-term outcomes of these treatments in patients with refractory or unexplained chronic cough.

The goal of this single-cohort clinical trial is to learn whether a smartphone-based Cough Management (CM) program can reduce cough frequency and burden in adults (21-80 years) who have refractory or unexplained chronic cough.  The main questions it aims to answer are: * Does four weeks of using the CM feature in the CoughPro app lower objective cough rate (coughs per hour) compared with each participant's one-week baseline?  * Does the program also lessen cough intensity (bout metrics) and improve patient-reported quality-of-life scores on the Leicester Cough Questionnaire and PGI-S? Participants will: * Wear a Hyfe CoughMonitor smartwatch continuously for 6 weeks (1-week baseline, 4-week intervention, 1-week follow-up), charging it nightly.  * Complete science-based in-app CM lessons based on behavioral cough-suppression therapy and practice the techniques during the 4-week intervention. * Fill out online questionnaires (LCQ and PGI-S) at baseline and at the end of Week 4. * Join a brief exit interview, then return the smartwatch and receive a compensation voucher.