Person-first language (PFL) prescribes the use of phrases like "a person with alcoholism" in preference to "an alcoholic" or "an alcoholic person". The idea is that separating the person from the affliction linguistically should accomplish the same in the minds of the speakers and listeners. Contrast with identity-first language (IFL), "an alcoholic person".
Wikipedia lists a variety of recommendations from a variety of groups in favor of person-first language, and a few in opposition (notably, the National Federation of the Blind, the deaf community, and the Autistic Self Advocacy Network). It is short on experimental results, though.
Fernandes et al. (2009) studied 214 academically gifted Brazilian Portuguese-speaking high school students. The students were split into two groups and given a survey to determine attitudes towards people with epilepsy. Students asked about "a person with epilepsy" showed a lower degree of perceived stigma than those asked about "an epileptic". However, when Noble and Marson (2016) attempted to replicate this result with speakers of English in the UK, they found no statistically significant differences in attitudes between the groups.
Collier (2012) reports little difference between PFL and IFL:
Dietrich et al. (2001) found no significant difference between 544 college students' perceptions of a "stutterer" or "noun + who stutters".
Botha et al. (2021) suggest that the mental separation of autism from the person (the goal of PFL) may contribute to the incidence of "altruistic filicide", in which parents kill their children to, for example, 'free' them from autism (in 54% of studied cases deemed 'altruistic', the children killed were autistic). This is mere speculation, however.
Gomes (2018) finds that "without previous knowledge of PFL, it has no effect on perceived inclusivity".
Botha et al. (2021) reject the use of the term "person with autism", because "a not insubstantial body of literature is showing that this is both least preferred and most offensive, and there are more preferred, and less offensive alternatives available".
Collier (2012) reports:
On a survey of 638 people with epilepsy and 333 "significant others" (mostly parents), 86.7% and 93.4%, respectively, favored PFL (Noble et al., 2017).
Gernsbacher (2017) indicates that "person-first language is used more frequently to refer to children with disabilities than to refer to children without disabilities; person-first language is more frequently used to refer to children with disabilities than adults with disabilities; and person-first language is most frequently used to refer to children with the most stigmatized disabilities. Therefore, the use of person-first language in scholarly writing may actually accentuate stigma rather than attenuate it".
Crocker and Smith (2019) report that though pervasive in academia, person-first language is uncommon in practice.
Titchkosky (2001) (in a paper which is primarily about a Canadian government document, In Unison: A Canadian Approach to Disability Issues) generally rejects PFL as portraying the disabled as a shapeless mass of 'people', no different from anyone else, except in the variety of their disabilities. In other words, it in fact fails to put the person first.
Hoffman et al. (2020) give some statistics from a survey of college students, whether they know what PFL is, whether they think it is important, etc. The article makes gestures toward maybe there will be other ways that are better in the future and we should refer to people as they prefer, and Hoffman et al. acknowledged (and did not refute) claims that disabled persons tend to prefer IFL, but the overall tone is clearly in favor of PFL as the One True Way.
Flink (2021) makes a few unfounded statements about the effect of PFL, and concludes that even if disabled people prefer to use IFL, we should use PFL, since it's already the standard.
Dunn and Andrews (2015) give a good overview of the issue. They observe: "Diverse opinions regarding the use of person-first or identity-first language are likely to persist. The APA promotes use of person-first language, whereas researchers in disability studies encourage use of identity-first language. Some disabled people choose one over the other, whereas others respond to either or use them interchangeably".