The third scald­ing show­er be­fore break­fast was not for clean­li­ness. It was the on­ly place the young man stopped vom­it­ing. There was a cy­cle of blood tests, drips, in­jec­tions for nau­sea, en­doscopy and ab­dom­i­nal scans that yield­ed lit­tle use­ful in­for­ma­tion. The hot-wa­ter be­hav­iour is such a pe­cu­liar clin­i­cal clue that it un­locked the di­ag­no­sis like an episode of House, MD Some pa­tients dis­cov­er it by ac­ci­dent and then bathe com­pul­sive­ly be­cause the re­lief is so strik­ing.

The “Cannabi­noid Hy­per­eme­sis Syn­drome” (CHS) is an odd en­ti­ty. Cannabis (mar­i­jua­na, gan­ja or “weed”) can re­duce nau­sea and may be used med­i­c­i­nal­ly. Yet, in some peo­ple, pro­longed fre­quent use pro­duces the op­po­site: re­peat­ed at­tacks of se­vere nau­sea, ab­dom­i­nal pain and re­lent­less vom­it­ing. Heat may af­fect path­ways in­volved in tem­per­a­ture reg­u­la­tion, pain and nau­sea.

CHS of­ten de­vel­ops in stages. At first, there may be mild ear­ly-morn­ing nau­sea, vague ab­dom­i­nal dis­com­fort or a fear of vom­it­ing. The per­son con­tin­ues eat­ing and func­tion­ing.

Cannabis may ap­pear to help, so use con­tin­ues or in­creas­es. Then comes the clas­sic hy­per­emet­ic phase: vom­it­ing again and again, some­times for hours or days. The pa­tient paces, curls up, groans and re­turns to the show­er. This is al­so not a cure and pro­longed hot bathing may wors­en de­hy­dra­tion when a per­son is al­ready los­ing flu­id through vom­it­ing.

De­hy­dra­tion can be­come dan­ger­ous. The kid­neys need blood flow. Potas­si­um and oth­er salts can fall, which could cause un­sta­ble heart rhythms. Se­vere retch­ing can in­jure the oe­soph­a­gus. Oc­ca­sion­al­ly, in­di­vid­u­als be­come con­fused, col­lapse or de­vel­op oth­er se­ri­ous com­pli­ca­tions.

The In­ter­net has found a crude nick­name for these at­tacks: “scromit­ing,” a mash-up of scream­ing and vom­it­ing. It is mem­o­rable but I do not par­tic­u­lar­ly like it.

Any­one who can­not keep flu­ids down, is pass­ing very lit­tle urine, be­comes faint or con­fused, vom­its blood, de­vel­ops se­vere per­sis­tent ab­dom­i­nal pain, chest pain, fever or dif­fi­cul­ty breath­ing needs ur­gent med­ical as­sess­ment.

Preg­nan­cy, di­a­bet­ic ke­toaci­do­sis, pan­cre­ati­tis, ap­pen­dici­tis, in­testi­nal ob­struc­tion, in­fec­tion and poi­son­ing do not dis­ap­pear mere­ly be­cause some­one us­es cannabis. There is no sin­gle blood test that an­nounces CHS.

Ear­ly at­tacks may be la­belled gas­troen­teri­tis or food poi­son­ing. Re­cur­rent cas­es may ac­cu­mu­late CT scans, ul­tra­sounds, en­do­scopies and a small phar­ma­cy of an­ti-nau­sea drugs. Re­sults re­turn nor­mal or non­spe­cif­ic. Some­one writes “drug-seek­ing” in the notes, and the next en­counter be­gins bad­ly be­fore the pa­tient even en­ters the room.

A per­son with CHS is nei­ther fool­ish nor nec­es­sar­i­ly ad­dict­ed. Many have used cannabis for years with­out trou­ble. Some use it for sleep, anx­i­ety, pain or nau­sea. Oth­ers sim­ply do not re­gard mar­i­jua­na as a drug worth men­tion­ing or avoid health care’s judge­ment.

In the emer­gency de­part­ment, treat­ment be­gins with in­tra­venous flu­id when nec­es­sary, cor­rec­tion of elec­trolyte dis­tur­bances and med­ica­tion for vom­it­ing or pain. Stan­dard an­ti-nau­sea drugs do not al­ways work well.

Doc­tors may use oth­er med­i­cines, in­clud­ing dopamine-block­ing agents, or top­i­cal cap­saicin un­der ap­pro­pri­ate su­per­vi­sion. The lat­ter ac­ti­vates heat-sen­si­tive path­ways and may mim­ic part of the hot-show­er ef­fect. None of these is a li­cence for home ex­per­i­men­ta­tion. Some have im­por­tant ad­verse ef­fects and re­quire clin­i­cal judge­ment.

The on­ly re­li­able long-term treat­ment is stop­ping cannabis. Com­plete ces­sa­tion al­lows the syn­drome to re­solve. Fre­quent users may ex­pe­ri­ence ir­ri­tabil­i­ty, poor sleep, anx­i­ety, re­duced ap­petite and crav­ings when they stop. Some are self-treat­ing grief, trau­ma or men­tal ill­ness. They need a plan, fol­low-up and, when ap­pro­pri­ate, coun­selling or ad­dic­tion sup­port.

Ear­li­er this month, the US Cen­ters for Dis­ease Con­trol and Pre­ven­tion pub­lished a re­port ex­am­in­ing emer­gency de­part­ment vis­its in­volv­ing CHS. The high­est pro­por­tions oc­curred among peo­ple aged 15 to 24 and women were rep­re­sent­ed more than many clin­i­cians might ex­pect.

Vom­it­ing in a young woman may be quick­ly at­trib­uted to preg­nan­cy, anx­i­ety, mi­graine or a stom­ach in­fec­tion. Cannabis use may nev­er be dis­cussed, or she may not vol­un­teer it be­cause she ex­pects a lec­ture rather than help.

This is not a moral­i­ty tale about cannabis or a claim that every­one who us­es mar­i­jua­na will de­vel­op the con­di­tion. CHS ap­pears to af­fect a sus­cep­ti­ble group of fre­quent users, and med­i­cine still does not ful­ly un­der­stand why one per­son be­comes ill while an­oth­er does not. The cannabi­noid sys­tem in­flu­ences the brain, gut, ap­petite, pain and tem­per­a­ture reg­u­la­tion. With sus­tained ex­po­sure, those ef­fects may be­come dis­or­dered. Po­ten­cy, fre­quen­cy, du­ra­tion and in­di­vid­ual bi­ol­o­gy prob­a­bly mat­ter. As we know, “nat­ur­al” is not a syn­onym for harm­less.

We al­so need bet­ter lo­cal recog­ni­tion. Emer­gency clin­i­cians should con­sid­er CHS in re­cur­rent un­ex­plained vom­it­ing, par­tic­u­lar­ly when cannabis use is fre­quent and hot wa­ter brings re­lief. Gen­er­al prac­ti­tion­ers should ask be­fore the third hos­pi­tal vis­it, not af­ter the tenth. Fam­i­lies should know the pat­tern while youths should hear about it with­out melo­dra­ma. The aim is to de­scribe a con­di­tion many have nev­er been told ex­ists.

Some­times the most use­ful med­ical clue lies in tak­ing a good his­to­ry. Why does the vom­it­ing stop in a hot show­er?

Ask the next ques­tion. Ask about cannabis.