It is often argued that a benefit of religion is the physical and mental well being of its adherents, therefore, religion is good and no one should argue for its disappearance. Yes, religion often does some good things, though as I’ve always argued, religion is responsible for far more bad and immoral things than good and that shouldn’t be forgotten. The simple fact is that religion is not needed to lead a perfectly happy and fulfilling life and there are many studies to back that up. The fact is that nontheists simply make use of other means to ease their stress and hardships. Many theists pray and go to church for comfort. Many nontheists gather with friends and family for guidance, but also realize the fact that there is no magic man in the sky to ease ones’ problems. With the following studies I hope to shed light on issues related to the emotional well-being of atheists, compared to theists, such as tolerance, open-mindedness, happiness, etc.
There are several studies that have sought to determine which group (whether theists or atheists) is most tolerant of others. One such study was conducted throughout the years 1973-1985, and published in 1988, which showed that “disaffiliation from religious dominations contributed to greater political liberalism”,  and a 1968 study of 1,500 freshmen at thirty-seven American colleges showed that the individuals who supported more liberal ideas (such as a welfare state, organized labor, social change towards greater equality) the nonreligious and Jews  scored highest, while Protestants scored the lowest.  In addition, a 1950 study of ethnocentrism and anti-Semitism showed that respondents having no religious affiliation had much lower levels of prejudice. The authors of the study summed up their findings as such:
“[I]t appears that those who reject religion have less ethnocentrism tha[n] those who seem to accept it.”  (A likely typo has been corrected by me)
Many studies have also confirmed that those who are more religious are less tolerant of deviates. Since the 1940’s the results have continuously shown that people who scored high on the “religionism” factor had more punitive attitudes towards criminals, homosexuals, and unmarried mothers. Overall, it’s been shown that those who are more religious are more intolerant, the irreligious and Jews, more tolerant. 
As far as atheists having a good state of mind, a study in 1995 showed that “the non-religious are psychologically healthier than religious individuals and […] this may be related to ‘a sense of personal competence and control, self-acceptance and self-actualization, and perhaps open-mindedness and flexibility.'” 
Another study done by Bruce E. Hunsberger and Bob Altemeyer in 2002 analyzed answers from several hundred atheists and theists United States and Canada and examined a number of personality traits and beliefs. 
Such things Hunsberger and Altemeyer compared were issues of dogmatism, ethnocentrism, and zealotry, among others. As far as dogmatism, on a scale with the lowest score being 20; the highest, 180. The American atheists sampled scored an 88, while the Canadian atheists scored a 65. While these numbers look somewhat bad for the atheists sampled, the fundamentalist christians scored a total of 126. Of course the researchers also caution that the American atheists’ high test scores were likely do to the average ages of the atheists sampled. To quote the researchers:
“Why did the American atheists score as high as they did? We have to cut them some slack here because they have celebrated about a dozen more birthdays than the Manitoba [Canadian] parents. So items such as ‘Someday I will probably realize my present ideas about the BIG issues are wrong,’ ‘I am a long way from reaching final conclusions about the central issues in life,’ and ‘Twenty years from now, some of my opinions about the important things in life will probably have changed’ probably mean something a little different to a person who is sixty than they do to one who is forty-eight.” 
Regarding zealotry, the researchers asked three questions to each group of theists and atheists. The first, if a teen would come to you about advice on religion, what would you say to him or her? Of the two American atheist groups 62% (San Francisco atheists) and 63% (Alabama/Idaho atheists) would have “said something to the troubled teen that would have promoted apostasy.” While 86% the Canadian atheists would simply tell the teen to do some searching and then decide what to believe themselves. 
The atheists were then asked whether or not they would want the teen to end up becoming an atheist, either through the atheists’ influence or their personal search. 53% of the San Francisco atheists, as well as 48% of the Alabama and Idaho atheists answered “yes” they would like to see the teen choose their way of thinking. However, regarding the question of whether or not they would attempt to lead the teen in the direction of their own beliefs 42% of the San Francisco atheists and 38% of the Alabama/Idaho atheists answered yes. Only 16% of the Canadian atheists said yes to the same question. 
However, when the theists were asked the same question, 88% said they would tell the teen they were wrong and should become more religious, while only 12% said they would advice the teen to “search and decide.”
On the second question asked, whether or not they would try to convince the teen to adopt their beliefs, 96% of the theists answered yes, and 98% said they would try to lead the teen in that direction. 
Clearly, when it comes to proselytizing, the theists are way ahead of the atheists.
The next question asked, one that is often a talking point regarding Richard Dawkins and what he labels “child abuse”, was whether or not the atheist and theist parents would want to raise their child in a religious environment and encourage their children to share the parents’ religious beliefs.
56% of the San Francisco atheists, and 44% of the Alabama/Idaho atheists reported that they would want their children to make up their own mind regarding religion. 86% of the Canadian atheists reported that they would want their children to make up their own minds. However, nearly all the fundamentalist christians (94%) said they would or have made a strong effort in passing their beliefs on to their children. 
This next question is also one that is often discussed, as many theists often foolishly accuse atheists of wishing their “godless” beliefs foisted upon children in public schools. 
The question asked was the following:
“Suppose a law were passed requiring strenuous teaching in public schools against belief in God and religion. Beginning in kindergarten, all children would be taught that belief in God is unsupported by logic and science, and that traditional religions are based on unreliable scriptures and outdated principals. All children would eventually be encouraged to become atheists or agnostics. How would you react to such a law?”
The answers available were:
1) I think it would be a bad law. No particular religious beliefs should be taught in a public school.
2) I think it would be a good law. These particular beliefs should be taught in public schools.
78% of the San Francisco atheists and 68% of the Alabama/Idaho atheists said this would be a bad law; all of the Canadian atheists were against this law.
However, with the theists, the numbers flipped (surprise, surprise!) when asked the above question, only reversed:
“Suppose a law were passed requiring the strenuous teaching of religion in public schools. Beginning in kindergarten, all children would be taught to believe in God, pray together in school several times each day, memorize the Ten Commandments and other parts of the Bible, learn the principles of Christian morality, and eventually be encouraged to accept Jesus Christ as their personal savior. How would you react to such a law?”
84% of the theists questioned thought that the above law would be a good one. 
An interesting question they posed to the atheists was whether or not they had secret doubts about their non-belief. They found that only 4% admitted to having “secret doubts”, while 92% said that they do not have any doubts and fully believe their public stand. While, in a previous study the authors did they found that one-third of the religious questioners admitted to having doubts. 
I find this aspect of the study very interesting. Very often atheism is defined by theists (ie. wrongly) as a delusion; as a belief there is no god, or a denial of such a being. Clearly, if anyone is in denial it is the theists when they are truly honest. No wonder the extreme hostility from so many theists when their beliefs are questioned (ie. the countless books attacking Richard Dawkins and his book The God Delusion). Whether or not they are conscious of it, all these theists must have some serious doubts and feel the need to lash out in anger when atheists point out the many flaws in their attempts at rationalizing their absurd beliefs.
Next, the authors discuss the issue of authoritarianism,  in which on the RWA (Right-Wing Authoritarianism) scale, the atheists scored a very low 51 (well on the unauthoritarian side of the neutral point of 100), while the theists scored a 135. 
Finally, I will cite the authors’ chart summarizing the findings regarding low RWA’s. 
Compared to others, persons who score on the low end of the RWA scale are significantly more likely to:
1. Condemn unfair and illegal abuses of power by government authorities.
2. Distrust leaders who are untrustworthy.
3. Defend constitutional guarantees of liberty, such as the Bill of Rights.
4. Punish the crime when sentencing criminals; administer justice fairly, regardless of who the criminal is.
5. Hold authorities who commit crimes and people who attack minorities responsible for their actions.
6. Not rely on physical punishment as a way to correct behavior.
7. Resist government pressure to help persecute target groups.
8. Be understanding of those who have made mistakes and suffered.
9. Have well-integrated, non compartmental minds.
10. Avoid using double standards in their judgments.
11. Not be hypocrites.
12. Be unprejudiced toward racial, ethnic, nationalistic, and linguistic minorities.
13. Accept homosexuals as people like anyone else and condemn “gay bashing.”
14. Support feminism.
15. Be less conforming to the opinions of others, and not be a yea-sayer, nor believe strongly in group cohesiveness and “group loyalty.”
16. Be aware of themselves. Realize their personal failings and be open to feedback about such failings.
17. Not trust someone merely because he tells them what they want to hear.
18. Not feel the world is a dangerous place nor be self-righteous.
19. Be non dogmatic and non zealous.
20. Support “liberal” or “left-wing” political parties and movements.
Another study done by Gary Leak and Brandy Randall in 1995 and published in the Journal for the Scientific Study of Religion “found that those who score high on the Right-Wing Authoritarianism scale have several tendencies. They are likely ‘to aggress against unpopular or unconventional groups, feel morally superior and self-righteous,’ and ‘possess a mean-spiritedness that is coupled with vindictiveness.’ They often take ‘secret pleasure’ when others experience misfortune and appear prejudiced toward out-groups.'”  It has been continuously demonstrated that those who are fundamentalists are most likely to possess authoritarian personalities.
The following information also shows how religion is not a necessity for moral behavior. In 1934, Abraham Franzblau found a negative correlation between acceptance of religious beliefs and three different measures of honesty. As religiosity increased, honesty decreased.
In 1950, Murray Ross conducted a survey among 2,000 associates of the YMCA and discovered that agnostics and atheists were more likely to express their willingness to aid the poor than those who rated themselves as deeply religious.
In 1969, sociologists Travis Hirschi and Rodney Stark reported no difference in the self-reported likelihood to commit crimes between children who attended church regularly and those who did not.
In 1975, Ronald Smith, Gregory Wheeler, and Edward Diener discovered that college-aged students in religious schools were no less likely to cheat on a test than their atheist and agnostic counterparts in nonreligious schools.
The July/August 2007 issue of the Annals of Family Medicine published the results of a study conducted by researchers from the University of Chicago and Yale New Haven Hospital that religious doctors were no more likely (and even slightly less likely) to employ their craft among underserved patients than were physicians with no religious affiliation. Specifically, Farr Curlin, MD, an assistant professor of medicine at the University of Chicago and his colleagues surveyed 1,820 practicing physicians from all specialties: 31% of physicians who were more religious practiced medicine among the underserved, compared to 35% of atheist, agnostic, and nonreligious doctors. Religiosity was measured by religious service attendance and self-reported “intrinsic religiosity” questions that measured the extent to which individuals embrace their religion as the “master motive that guides and gives meaning to their life.” Curlin noted his own response to the data:
“This came as both a surprise and a disappointment. The Christian, Jewish, Muslim, Hindu and Buddhist scriptures all urge physicians to care for the poor, and the great majority of religious physicians describe their practice of medicine as a calling. Yet we found that religious physicians were not more likely to report practice among the underserved than their secular colleagues.'” 
Also, according to the 2005 United Nations’ Human Development Report, European and other countries (such as Sweden, the Netherlands, the United Kingdom, Japan, Iceland, etc.) are the healthiest, as indicated by life expectancy, adult literacy, per capita income, educational attainment, gender equality, homicide rate, and are also the most charitable in terms of the percentage of their wealth they spend on welfare programs and for aid to the developing world. 
Finally, while there are many studies that do provide some evidence as to the health benefits of religion, such as less anxiety about death,  lower rates of tobacco and alcohol use, and depression,  there are about as many negative effects as well.
There are many studies, and many cases, showing that the devoutly religious often do not believe in modern medicine and other life-saving treatments. The spread of AIDS due to many religious doctrines prohibiting contraception (especially in Africa), prohibitions on stem-cell research, wherein lies potential cures for Parkinson’s disease, diabetes, etc. (though that theat is largely gone now thanks to the president Obama’s administration, though who knows what the future holds if the religious get their way again…). Due to some religious denominations it is against their beliefs to get abortions, which if a pregnancy gone wrong occurs it can sometimes kill the mother if she doesn’t believe in the sometimes life-saving operation. There is also ample research suggesting that a percentage of religious individuals practice out-of-hospital, non-physician attended birthing without any form of prenatal care. 
For example, a religious group called Faith Assembly has no medical or prenatal care and in Indiana zero percent of the Faith Assembly subjects had at least one prenatal visit compared to 99 percent for the non-Faith Assembly women. Perinatal mortality was three times greater and maternal mortality was almost 100 times greater in Faith Assembly women compared to non-Faith Assembly women. 
Christian Scientists who rarely consult doctors is another example. Age-adjusted death rates were significantly higher (p = .003) in Christian Science women than non-Christian Science women. 
I’ve done my best to find a variety of studies proving how religion is not needed to live a happy life and be a well adjusted and healthy individual. In fact, as was seen throughout many of these studies religion can have a negative impact on society and well-being. While this paper outlines many years worth of research there is much more one can examine.  I suggest the reader, if it interests him or her, to seek out these other sources.
1. The Cambridge Companion to Atheism, edited by Michael Martin, Cambridge University Press, 2007; 303
2. Most Jews are some of the most secular of religious individuals, which would explain the similar study results.
According to a 2003 Harris Poll, “Only 16 percent of Jews go to synagogue once a month or more often”; and regarding belief in God: “Protestants (90 percent) are more likely than Roman Catholics (79 percent) and much more likely than Jews (48 percent) to believe in God. Religious affiliation here includes many people raised as members of a religion or religious group, regardless of what they practice or believe now.” – Explaining Jews, Part II: Why Are Most Jews Secular?, By: Dennis Prager
3. The Cambridge Companion to Atheism, edited by Michael Martin, Cambridge University Press, 2007; 303
4. Ibid. 304
5. Ibid. 305
6. Ibid. 306
7. Atheists: A Groundbreaking Study of America’s Nonbelievers, by Bruce E. Hunsberger & Bob Altemeyer, Prometheus Books, 2006; 23-33
8. Ibid.; 62
9. Ibid.; 70
10. Ibid..; 70-71
11. Ibid.; 71
12. Ibid.; 72-73
13. Indoctrination by Our Public Schools, by Jerry Bergman
14. Atheists: A Groundbreaking Study of America’s Nonbelievers; 73-74
15. Ibid.; 90-93
16. Right-Wing Authoritarianism is defined as the covariation of three kinds of attitudes: authoritarian submission (to established authorities), authoritarian aggression (against anyone the authorities target), and conventionalism (adhering to the social conventions thought to be endorsed by society and the established authorities).
17. Atheists: A Groundbreaking Study of America’s Nonbelievers; 97
18. Ibid.; 110
19. The Fundamentals of Extremism: The Christian Right in America, Edited by Kimberly Blaker, New Boston Books, Inc., 2003; 38
21. Letter to a Christian Nation, by Sam Harris, Alfred A. Knopf, 2006; 43-46
22. Many reports make this claim, though it seems this isn’t always true, as Phil Zuckerman found out when conducting interviews for his book Society Without God in Scandinavia. He interviewed a woman named Anne who is a hospice nurse and she reported that the christians have the most fear of death; fear of whether or not they will go to heaven or hell, and thinking about their life; had they done anything wrong and feeling guilty (pg. 46).
23. Did Man Create God? Is Your Spiritual Brain at Peace with Your Thinking Brain?, by David E. Comings, M.D., Hope Press, 2008; 604-611
24. Ibid.; 599
25. Ibid.; 599
26. Ibid.; 599
27. Two examples are: Phil Zuckerman’s Society without God: What the Least Religious Nations Can Tell Us about Contentment, published by New York University Press, 2008
Zuckerman has also written a paper titled Atheism, Secularity, and Well-Being: How the Findings of Social Science Counter Negative Stereotypes and Assumptions (2009) which is much more detailed in refuting the oft used claim that religion is a necessary component to a happy society and well-being.