Hi! I have 10 years of experience in psychiatry which actually started after I had a few hospitalizations myself and found out a place was hiring. I've specifically worked in the more acute environments including my first job placing me on an all-male forensic unit with men concurrently facing criminal charges and being evaluated for competency to stand trial. Even after that I've continued working in other high acuity environments with civil / non-forensic patients. I'm kind of an expert at this point on violence management in the acute inpatient environment and often joke that I'm the closest psychiatry gets to being an intensive care unit nurse (if only I could have their nurse/patient ratio!
I actually have a LOT of reasons I have to do those kinds of searches for EVERY patient, but first I'd like to point out that I actually do NOT search patients to the same extent a jail or prison does. A jail or prison typically does cavity searches where they actually insert fingers inside the inmate's bodily cavities and of the half dozen facilities I have worked none of them have found the reduction in risk to be worth inserting fingers into patients. I'm hopeful for your future that you never actually experience a prison-level search. I typically also do not remove all articles of clothing at once or apply a drape over areas I am not actively inspecting to try to provide some dignity during the process. In the many years I've worked since my own hospitalizations I've come to realize that there are actually a lot of really important safety reasons that we NEED to search EVERY patient. Here are the main ones:
a) I need to know if you have weapons / self injury implements or drugs. We actually had a fentanyl overdose a few months ago and the patient had to be narcanned and sent out because someone didn't check the patient thoroughly enough. With substance abuse and violence to the self or others there's really no way to just look at someone and know what they're capable of so the only way to know for sure is to check. Even with a health history I can broadly estimate their lifetime risk of those things, but especially if it's their first manic or psychotic break, I genuinely have no idea what they're capable of until I've seen it for myself (also some of these other facilities in the health history be sketchy AF and will lie about shit). If someone is going to be violent to themselves or others I need them to be unarmed because it reduces the amount of damage they can do to both me and other patients and the likelihood that I will have to restrain them or even worse, decide between my life and my job and risk harming them in self-defense. Note that I also included other patients. The fact that ALL PATIENTS are being searched to this extent is making you safer by making sure a dangerous patient on the unit with you also does not have access to weapons.
b) you could also be carrying something that you wouldn't or even don't realize could be used as a weapon or implement of self injury. This could be something obvious like a multitool / swiss army knife or box cutter, or it could be something that would otherwise be completely benign like drawstrings or shoelaces (hanging / ligature risk or a garrote weapon), a screwdriver or pen, or a toothbrush soft enough to be sharpened. There are other items that can be used to modify the environment in harmful ways or to access areas with equipment that could be used, such as a paperclip as a lockpick. Just because YOU wouldn't use it that way doesn't mean another person wouldn't, and the inpatient environment you're describing has a lot of severely sick patients. And even if you're aware enough of your surroundings to not willingly give it to another patient, many patients are too unaware or too trusting, and some aggressors are extremely skilled thieves. We actually had a patient who was experienced with prison level searches recently who it turned out had taped a weapon under his scrotum and used it the very next day to harm someone.
c) Even beyond illicit substances we can't allow anything that would involve a flame or even a battery powered heating element such as tobacco or Marijuana, even as a vape. Every general hospital has pure oxygen running through the walls and even a standalone psych hospital has tanks on every unit for emergencies, and both can leak and we would never know because it's colorless and odorless. In addition, most supplies are going to use materials like pure cotton (prevents skin reactions) and paper (disposable, used as packaging for clean or sterile equipment), and petroleum jelly based medications and hygiene products and all of those are extremely flammable. While oxygen itself is not flammable, it decreases how much material and heat is needed to cause a bigger flame. A lot of deadly house fires are actually caused by smoking while on oxygen therapy, and planes forbid smoking for the same reasons. So if there is a spark, the whole unit is going up in flames before you know it, and unfortunately smokers often don't realize the risk of smoking in that environment. This can be because of altered mental status and not comprehending the risk or even realizing where they are, or it can just be because they're stubborn and highly dependent (heroin addicts have told me cigarettes are harder to quit).
d) you don't seem to realize that just because YOUR acuity wasn't high enough to require that search, many other inpatients are, especially if they're experiencing SEVERE psychosis and / or mania. Even if I could conclusively estimate your violence risk as low enough to safely have certain items, I still can't risk ANY other patient on the unit getting ahold of them.
e) the shower I can't speak to exactly because I've never worked a facility that does that but I can tell you we've had patients come in before with lice or fleas, or bedbugs in their belongings. This, and more especially contagious bacterial and fungal infections like MRSA are often not obvious and we cannot provide infectious isolation the same way a medical unit can. If you've never had MRSA or bedbugs (even having fleas permanently traumatized me in my own life), then you need to be grateful to your own luck and the hard work of your Healthcare staff to prevent the spread of profoundly life-altering infections.
f) I almost forgot! All hospitals these days are actually supposed to do a full body skin check! A regular hospital patient who is voluntary could be documented as having refused (but they also don't pose the same risks!) but we are actually supposed to check for fall and pressure injuries on admission! Fall and pressure injuries are actually reportable events and depending on the severity we can actually get in a LOT of trouble if we can't prove they were already there on admission. This is part of why most places require TWO licensed staff members (a CNA is only a cert!) to inspect all patients. This can affect minor things like billing (well, I think it's minor, my boss disagrees!) or if it's very severe even be grounds for malpractice. Self inflicted injuries during your stay are less likely to be determined as the facilitie's fault, but it's still possible.
Your difficulty understanding this situation also suggests to be that you yourself likely do not have a severe of a mental illness as my kind of facility is designed for. You may have been suited to a lower acuity program such as:
a) a Crisis Stabilization Unit (CSU), which is a similar level of care to a substance abuse rehab facility, but that also treats mental health conditions without substance abuse.
b) You maybe could have also visited an emergency room that includes a specialized Psych-ER (more common in large hospitals that have multiple / subdivided ER wings) which often serve the same acuity, but which usually only keep a patient for 24-48 hours, and sometimes don't search as thoroughly due to not having as many common areas.
c) There are also partial hospitalization programs (PHPs) and Intensive Outpatient Programs (IOPs) where you don't even stay overnight, you just go in during weekdays for classes.
d) You could also consider a Dialectal Behavior Therapy (DBT) program which is a completely outpatient program but a slightly higher level of care than just a once-weekly 1hr therapist appointment.
e) Another longer term option is Assertive Community Treatment (ACT) where the patient is followed over months or years by a complete team including an outpatient psychiatrist, social worker, and home-help psych nurse.
The downside is that due to the low (and steadily reducing) public funding for mental health services, and the financial toll mental illness often takes on the patients themselves, some of these programs are hard to find or access or have to dedicate themselves to specific types of patients. As an example, DBT is often reserved for personality disorders and ACT is often reserved for patients who have been hospitalized numerous times over an extended period and have been well proven to need additional community treatment. Often programs are also not available in rural or disadvantaged communities meaning you would have had to travel far away, or they just don't have enough beds / rooms to meet the needs of their community. So you likely did and do have other options that could be much better suited to your needs, but I can also understand that you may not have been aware of them or have had difficulty accessing them.
Hope this helps!