Editing Phobia (section)

==Causes==
Phobias may develop for a variety of reasons. Childhood experiences, past traumatic experiences, brain chemistry, genetics, or learned behavior, can all be reasons why phobias develop. There are even phobias that may run in families and be passed down from one generation to another.<ref>{{Cite journal |last=Garcia |first=René |date=2017-09-01 |title=Neurobiology of fear and specific phobias |url=http://learnmem.cshlp.org/content/24/9/462 |journal=Learning & Memory |language=en |volume=24 |issue=9 |pages=462–471 |doi=10.1101/lm.044115.116 |issn=1072-0502 |pmid=28814472|pmc=5580526 }}</ref>

There are multiple theories about how phobias develop and likely occur due to a combination of environmental and genetic factors. The degree to whether environment or genetic influences have a more significant role varies by condition, with social anxiety disorder and agoraphobia having around a 50% heritability rate.<ref name=":1" />

===Environmental===
Rachman proposed three pathways for the development of phobias: direct or classical conditioning (exposure to phobic stimulus), vicarious acquisition (seeing others experience phobic stimulus), and informational/instructional acquisition (learning about phobic stimulus from others).<ref>{{cite book | vauthors = Rachman SJ |title=Fear and Courage |year=1978 |publisher=WH Freeman & Co. |location=San Francisco}}</ref><ref name=":0">{{cite journal | vauthors = King NJ, Eleonora G, Ollendick TH | title = Etiology of childhood phobias: current status of Rachman's three pathways theory | journal = Behaviour Research and Therapy | volume = 36 | issue = 3 | pages = 297–309 | date = March 1998 | pmid = 9642849 | doi = 10.1016/S0005-7967(98)00015-1 }}</ref>

==== Classical conditioning ====
Much of the progress in understanding the acquisition of fear responses in phobias can be attributed to [[classical conditioning]] (Pavlovian model).<ref name="ProQuest Health and Medical Complete">{{cite journal | vauthors = Myers KM, Davis M | title = Mechanisms of fear extinction | journal = Molecular Psychiatry | volume = 12 | issue = 2 | pages = 120–150 | date = February 2007 | pmid = 17160066 | doi = 10.1038/sj.mp.4001939 | s2cid = 3364934 | id = {{ProQuest|221163409}} | doi-access =  }}</ref> When an aversive stimulus and a neutral one are paired together, for instance, when an electric shock is given in a specific room, the subject can start to fear not only the shock but the room as well. In behavioral terms, the room is a [[conditioned stimulus]] (CS). When paired with an aversive [[unconditioned stimulus]] (UCS) ''(the shock)'', it creates a [[conditioned response]] (CR) ''(fear for the room)'' (CS+UCS=CR).<ref name="ProQuest Health and Medical Complete"/> For example, in case of the fear of heights ([[acrophobia]]), the CS is heights. Such as a balcony on the top floors of a high rise building. The UCS can originate from an aversive or traumatizing event in the person's life, such as almost falling from a great height. The original fear of nearly falling is associated with being high, leading to a fear of heights. In other words, the CS ''(heights)'' associated with the aversive UCS ''(almost falling)'' leads to the CR ''(fear)''.
It is possible, however, to extinguish the CR, and reversing the effects of the CS and UCS. Repeatedly presenting the CS alone, without the UCS, can exinguish the CR.<ref>{{Cite journal |last=Vurbic |first=Drina |date=September 2011 |title=Secondary extinction in Pavlovian fear conditioning |journal=Learning & Behavior |volume=39 |issue=3 |pages=202–211 |doi=10.3758/s13420-011-0017-7 |pmid=21286897 |pmc=3117985 }}</ref>

Though historically influential in the theory of fear acquisition, this direct conditioning model is not the only proposed way to acquire a phobia. This theory in fact has limitations as not everyone that has experienced a traumatic event develops a phobia and vice versa.<ref name=":0" />

==== Vicarious conditioning ====
Vicarious fear acquisition is learning to fear something, not by a subject's own experience of fear, but by watching others, oftentimes a parent ([[observational learning]]). For instance, when a child sees a parent reacting fearfully to an animal, the child can also become afraid of the animal.<ref>{{cite web | url=http://behavenet.com/vicarious-conditioning | title=vicarious conditioning | publisher=BehaveNet | access-date=2013-06-21 }}</ref> Through observational learning, humans can learn to fear potentially dangerous objects—a reaction observed in other primates.<ref name="Snakes">{{cite journal | vauthors = Mineka S, Davidson M, Cook M, Keir R | title = Observational conditioning of snake fear in rhesus monkeys | journal = Journal of Abnormal Psychology | volume = 93 | issue = 4 | pages = 355–372 | date = November 1984 | pmid = 6542574 | doi = 10.1037/0021-843x.93.4.355 }}</ref> A study on non-human primates, showed that the primates learned to fear snakes at a fast rate after watching parents' fearful reactions.<ref name="Snakes"/> An increase in fearful behaviours was observed as the non-human primates observed their parents' fearful reactions.<ref name="Snakes"/> Although observational learning has proven effective in creating reactions of fear and phobias, it has also been shown that by physically experiencing an event, increases the chance of fearful and phobic behaviours.<ref name="Snakes"/> In some cases, physically experiencing an event may increase the fear and phobia more than observing a fearful reaction of another human or non-human primate.

==== Informational/Instructional acquisition ====
Informational/instructional fear acquisition is learning to fear something by getting information. For instance, fearing electrical wire after hearing that touching it causes an electric shock.<ref>{{cite journal | vauthors = Olsson A, Phelps EA | title = Learned fear of "unseen" faces after Pavlovian, observational, and instructed fear | journal = Psychological Science | volume = 15 | issue = 12 | pages = 822–828 | date = December 2004 | pmid = 15563327 | doi = 10.1111/j.0956-7976.2004.00762.x | url = http://www.psych.nyu.edu/phelpslab/papers/OlssonPhelps_PsychSc.pdf | url-status = live | s2cid = 13889777 | archive-url = https://web.archive.org/web/20131109133316/http://www.psych.nyu.edu/phelpslab/papers/OlssonPhelps_PsychSc.pdf | archive-date = 2013-11-09 }}</ref>

A conditioned fear response to an object or situation is not always a phobia. There must also be symptoms of impairment and avoidance. Impairment is defined as an inability to complete routine tasks, whether occupational, academic, or social.  For example, an occupational impairment can result from acrophobia, from not taking a job solely because of its location on the top floor of a building, or socially not participating in an event at a theme park. The avoidance aspect is defined as behaviour that results in the omission of an aversive event that would otherwise occur, intending to prevent anxiety.<ref>{{cite journal| vauthors = Bolles RC |title=Species-specific Defense Reactions and Avoidance Learning|journal=Psychological Review|year=1970|volume=77|pages=32–38|doi=10.1037/h0028589}}</ref>

=== Genetic ===
{{Main|Epigenetics of anxiety and stress–related disorders}}
With the completion of the [[Human Genome Project]] in 2003, much research has been completed looking at specific genes that may cause or contribute to medical conditions.<ref>{{Cite web |title=Human Genome Project FAQ |url=https://www.genome.gov/human-genome-project/Completion-FAQ |access-date=2022-03-11 |website=Genome.gov |language=en}}</ref> Candidate genes were the focus of most of these studies until the past decade, when the cost and ability to perform genome-wide analyses became more available. The GLRB gene was identified as a possible target for agoraphobia.<ref>{{cite journal | vauthors = Deckert J, Weber H, Villmann C, Lonsdorf TB, Richter J, Andreatta M, Arias-Vasquez A, Hommers L, Kent L, Schartner C, Cichon S, Wolf C, Schaefer N, von Collenberg CR, Wachter B, Blum R, Schümann D, Scharfenort R, Schumacher J, Forstner AJ, Baumann C, Schiele MA, Notzon S, Zwanzger P, Janzing JG, Galesloot T, Kiemeney LA, Gajewska A, Glotzbach-Schoon E, Mühlberger A, Alpers G, Fydrich T, Fehm L, Gerlach AL, Kircher T, Lang T, Ströhle A, Arolt V, Wittchen HU, Kalisch R, Büchel C, Hamm A, Nöthen MM, Romanos M, Domschke K, Pauli P, Reif A | display-authors = 6 | title = GLRB allelic variation associated with agoraphobic cognitions, increased startle response and fear network activation: a potential neurogenetic pathway to panic disorder | journal = Molecular Psychiatry | volume = 22 | issue = 10 | pages = 1431–1439 | date = October 2017 | pmid = 28167838 | doi = 10.1038/mp.2017.2 | hdl = 10023/11399 | s2cid = 10177012 | hdl-access = free }}</ref> An area still in development is reviewing [[Epigenetics|epigenetic]] components or the interaction of the environment on genes through methylation. A number of genes are being examined through this epigenetic lens which may be linked with social anxiety disorder, including MAOA, CRHR1, and OXTR.<ref name=":1" /> Each phobia related disorder has some degree of genetic susceptibility. Those with specific phobias are more likely to have first degree relatives with the same specific phobia. Similarly, social anxiety disorder is found two to six times more frequently in those with first degree relatives that have it versus those that do not. Agoraphobia is believed to have the strongest genetic association.<ref name="DSM5Social" /><ref name=":1" />