Throughout history, animals have played a significant role in society including in agriculture and pet ownership. A recent survey conducted in the United States estimated that approximately 67% of homes had at least one pet, equaling about 63 million homes with at least one dog and 42 million homes with at least one cat [1]. Pets can constitute a connection to nature, function in recreational and work activities, and provide companionship in our homes ^[2][3][4][2,3,4]. The importance of animals in our lives is founded on the human–animal bond concept, which is the “mutually beneficial and dynamic relationship that exists between people and other animals that is influenced by behaviors that are essential to the health and well-being of both” [5]. This concept has championed animals as companions and family members, leading to their essential part of everyday life for many. The human–animal bond has additionally driven the common belief that pets are good for human health, both physical and mental ^[6][7][8][6,7,8].

While there are some qualitative ^[9][10][9,10] studies that claim that pet ownership benefits people, particularly in regard to improved mental health, there are few studies with substantial evidence from large, diverse population samples to support this theory. The studies that have been published are often not substantiated with regard to study populations or methods, making broad conclusions difficult. Furthermore, some studies that have investigated the correlation between pet ownership and mental health have revealed no effect, or even worse, negative effects of pet ownership ^{[11][12][13][14][15]}[11,12,13,14,15].

Population Studied	Negative Impact	Mixed Impact	Positive Impact	No Impact	Total

Older adult
1
3	3	1	8 (61%)
Illness (cancer, back pain, etc.)		1			1 (8%)
Adults living alone	1				1 (8%)
Totals	2 (15%)	4 (31%)	5 (38%)	2 (15%)	13

Understanding the nature of the relationship between mental health and pet ownership is important for both human and animal welfare and to better determine the impact of human–animal interactions. Over the years, the perspective that “pets are good for you” has become an assumption ^[22][25] and when negative implications are recognized it often relates to zoonotic diseases rather than human–animal interactions ^[23][26]. This belief in the positive aspects of the human–animal bond is strengthened by marketing tools used by the pet industry ^[24][27]. While there certainly is evidence that supports the benefits of the human–animal bond to people’s mental health ^[25][26][28,29], there is also clear and consistent evidence that the relationship is complex and sometimes negative ^[27][28][30,31]. The question of whether pets should be prescribed by health professionals is an especially important one. Recent qualitative research supports that attending to a pet can help a person manage mental health crises ^[29][32], however, doing so can also cause a person to rely on the pet instead of other evidenced based methods of seeking mental health support. The recommendation of obtaining a pet in the presence of mental illness ought to be coupled with other evidenced based strategies for mental health recovery such as increasing social support and engaging in third wave behaviorally based interventions such as Acceptance and Commitment Therapy or Dialectical Behavior Therapy.

The broad perspectives that pets are good for mental health may cause people to place false expectations on the role a dog or cat must play in their lives ^[30][33]. The anthropomorphism of pets (people placing human cognitive motivations on pets’ behavior and treating pets as people) can in fact have a negative impact on the animal’s welfare ^[31][34]. The untreated stress of people who turn to their pets instead of their human social supports and health professionals may in fact be causing pets to be more stressed ^[32][35]. Although initial data suggest relinquishment rates were not higher after COVID-19 lockdowns were lifted ^[33][36], some still have concerns that the recent increase in pet adoptions from shelters may result in pet relinquishment once the pandemic is more managed and people return to their daily work environments ^[34][37] (J. Schumacher personal communication, 5 May 2021). Developing clear guidelines about the benefits and liabilities of pet ownership and mental health is important to mitigate the public halo effect that suggests that simply acquiring a pet will improve your mental health.