Mental health advocates have condemned Texas’ new firearms law for allowing the open carry of guns in state psychiatric hospitals, arguing it could negatively impact patients’ treatments and could lead to an uptick in suicide rates.

The state hospital in Austin took down its signs banning guns this week, the Austin American-Statesman reported, though officials have requested that if visitors enter with their weapons, they at least keep them hidden.

“With the new law in effect, we are putting up signs asking licensed gun holders to conceal their firearms or leave them safely in their vehicles before going into our state mental health hospitals,” said Carrie Williams, a spokeswoman for the state health department. “While licensed visitors are legally permitted to carry on our hospital campuses, our patients are being actively treated for psychiatric conditions and generally it’s best not to expose them to weapons of any kind.”

On New Year’s Day, Texas became the 45th and most populous state to allow some form of open carrying of handguns. Open display of long guns such as rifles was already legal, though a rarely-exercised right. The law repurposes concealed handgun licenses as “licenses to carry”, meaning that licensed Texans may now visibly carry guns in hip or shoulder holsters in many public places.

Greg Hansch, the public policy director of the Texas branch of the National Alliance on Mental Illness, said his group is opposed to people bringing guns onto state psychiatric hospital grounds, arguing that “it fosters fear and will be detrimental to the recovery of persons receiving treatment.

“The direction that state legislators and the governor are going in now is increasing the visibility and the availability of guns at state hospitals and that makes it more likely that the weapons will end up in the wrong hands.”

Hansch added that he is worried that allowing guns in mental hospitals will make it easier for suicidal people to kill themselves. Of the roughly 30,000 gun deaths in the US each year, around two-thirds are ruled suicide.

A loophole that was not closed when the new law passed last summer means that psychiatric institutions are not subject to the same exemption as general hospitals because they are in a different section of the state’s health and safety code.

Kirk Watson, a Democratic state senator, tried to address the apparent oversight last year in the legislature but said that the amendment he proposed was shut down without a debate, with Republicans unwilling to compromise. During their election campaigns and since taking office, many senior Texas politicians, including the governor, Greg Abbott, have pledged to expand gun rights. A concealed “campus carry” bill becomes law in August and will mean it is fine to bring a Glock into a public university’s dorm room – but not a waffle-maker.

“Part of the reason [the loophole] didn’t get closed is because of the desire to pander to a small but vocal group,” Watson said. “There’s some irony here because many who oppose reasonable restrictions on guns will often say that what we need is to have better mental healthcare … it’s just no place for people walking around with open weapons.”

More than 800,000 Texans are licensed out of a population of about 27 million. They must be older than 21, undergo four to six hours of training and take tests and background checks.

The law still prohibits firearms in certain sensitive locations, such as schools, courthouses, prisons, sports events and bars. Private businesses such as supermarkets and restaurants can choose to opt out, either by verbally informing customers that guns are unwelcome or by clearly posting standardised signs in English and Spanish at their entrances.

Some church pastors and even banks have said they are allowing the practice. But the law’s various exceptions and conditions have prompted confusion, especially related to multipurpose government and other public buildings, where weapons may be permitted in some places but not others.

The Houston Independent school district posted guidance advising community members that guns can be carried in school parking areas and driveways, “but only during times when a school-sponsored activity is not being conducted in the parking lot, driveway, or other parking area. If the school parking lot is used for band practice after school, handguns/firearms or other prohibited weapons cannot be carried openly or concealed in that parking lot when the band is practicing”.

Zoos have proved contentious, with several that are privately-funded but located on public land arguing they are exempt; the Houston zoo argues that it should be treated as an educational institution.