Problem gambling can have considerable negative impact on people’s lives [1]. Reportedly, the worldwide rates of lifetime problem gambling fall between 0.7 and 6.5% [2]. In Japan, a nationwide prevalence study revealed that approximately 1.5% of participants were classified as likely problem gamblers [3]. One of the essential characteristics of gambling in Japan is the type of gambling available. In Yokomitsu et al.’s [4] study, pachinko and slot machines (called pachislot in Japan) were the most common types of gambling activities engaged in by university students. In addition, Shoun et al. conducted a questionnaire study on 5,060 Japanese adults aged 18–79 years using a low-coverage error sampling method and found that 11.5% of participants (n = 582) had played pachinko or pachislot in the past 12 months [5]. Furthermore, the 9,000 slot machines and pachinko gambling venues in Japan make gambling highly accessible.
Pachislot, a popular type of gambling in Japan, is similar to casino slot machines that use cash. In Japan, players play pachislots using medals which also called tokens, which can be exchanged for cash. An important difference between pachislots in Japan and slot machines in overseas casinos is that the former is a player-participation type of gambling that requires the player to pull a lever on the side of the machine, push three buttons to stop a rolling reel, and align various symbols. A set of these processes is a game (play) in a pachislot. Players have the chance to win a large prize (nearly a jackpot) with a fixed probability for each game. Although this probability varies according to the type of pachislot, a one-in-two hundred chance is frequently applied. In each game, an animation with lights, sounds, and images is generated on a 14-inch (35.6 cm) liquid crystal display on the top of the reel. Large and loud animations signal a high probability of a big win. These animations include video gaming, which can immerse players in the gambling.
In contrast, pachinko, which is also popular in Japan, resembles a vertical pinball machine. A pachinko machine uses numerous pachinko balls, each approximately 1 cm in diameter. When a ball enters a catcher near the bottom center of the playing board, a big win is generated with a fixed probability. Similar to pachislot, the probability varies according to the kind of pachinko; however, a one-in-300 chance is frequently applied. The animations, with images, sound, and light production, in pachinko are the same as in pachislot wherein a large and loud production is associated with a high probability of a big win. However, in both pachislot and pachinko, gamblers sometimes do not achieve a big win, despite a pompous production. Such an event is called a near-miss event.
Problem gambling can lead to a variety of harms. In Langham et al.’s [6] review, gambling-related harm is defined as “any initial or exacerbated adverse consequence due to an engagement with gambling that leads to decrement to the health or well-being of an individual, family unit, community or population.” This review identified harms that could occur either sequentially or simultaneously. These types of harm include financial, interpersonal, emotional or psychological, health-related, professional, educational, and criminal harms. To reduce these harms, international guidelines recommend implementing evidence-based and best practice policies to minimize gambling, including specific requirements for policies on internet gambling. These guidelines include a minimum legal age of 18 years for gambling participation, licensing of gambling venues and activities with responsible gambling, and mandated consumer protection strategies. Additionally, brief interventions should be available for those susceptible to or facing gambling-related harm. Several harm-minimization strategies have been devised to prevent pathological gambling behaviors and facilitate self-control with respect to gambling [7]. These strategies include supply-reduction (reducing opportunities for gambling and providing low-investment gambling machines), demand-reduction (education to raise awareness about the potential harms of serious gambling), and harm-reduction interventions (approaches to reduce gambling-related harm, such as personalized normative feedback) [8, 9].
Although studies on approaches and policies to minimize gambling-related harm have been conducted, research related to harm reduction is still nascent in Japan. For example, some of the harm-minimization strategies and policies currently in place in Japan include pre-commitment/limits on the purchase of online horse race tickets upon application by an individual or a family member, removal of ATMs from horse, bicycle, and boat race tracks, setting limits on ATM withdrawals at pachinko venues (e.g., maximum \30,000 per day), and self-exclusion from pachinko venues on behalf of the applicant or a family member. In an earlier study conducted overseas [10], slot machines with a maximum stake of $1 (a low-investment gambling machine) were reported to reduce playing time, financial loss, and consumption of alcohol and cigarettes while gambling. This suggests that this type of low-investment gambling could also lead to harm reduction in Japan. Low-investment gambling in Japan is known as quarter-pachinko/pachislot (called ichi-yen pachinko/go-yen pachislots in Japan) and half-pachinko/pachislot (called ni-yen pachinko/ju-yen pachislots in Japan). Quarter-pachinko/pachislot is gambling at one-quarter the cost of regular pachinko/pachislot, while half-pachinko/pachislots is gambling at one-half the cost of regular pachinko/pachislot.
In the present study, we defined low-investment pachinko and pachislot as playing pachinko and pachislot for half or one quarter of the normal cost. Gamblers who played pachinko/pachislot for half of the normal cost were called “half-pachi players,” and those who played for a quarter of the normal cost were called “quarter-pachi players.” We categorized gamblers who played for the normal amount money as “normal-pachi players.” Notably, when gamblers play low-investment pachinko and pachislot, they are able to play twice or even four times as long as normal pachinko and pachislot for the same amount of money. Additionally, as gamblers bet less in this type of gambling, they are only able to gain half or a quarter of the normal amount. Thus, low-investment pachinko/pachislot could be considered low-risk and low-return gambling. Based on previous studies [20], low-investment pachinko gamblers could face less-impactful versions of several of the harms faced by normal gamblers, including gambling-related behaviors such as playing time and loss. However, it is unclear whether quarter- pachinko/pachislot and half- pachinko/pachislot would be effective in reducing gambling-related harms.
Therefore, we aimed to explore the effect of these low-investment types of pachinko/pachislot on gambling-related harms in adult gamblers in Japan. Specifically, we sought to compare gambling-related harms among normal-, half-, and quarter-pachi players. In the present study, we considered the following to be gambling related harms: player debt; the number of days players had gambled during the previous month; the total time and money spent on gambling; the severity of gambling; gambling cognitive distortion; depressive symptoms; and the degree of disability at work, home, and in players’ social lives. We hypothesized that half-, and quarter-pachi players would be less all gambling related harms than normal-pachi player.