These “pharmacokinetic and pharmacodynamic” descriptors of prayer are all important issues to judge from the manner in which persons pray, or if persons with strong religious affiliations are to be believed. Therefore, all of the above would need to be considered as independent or confounding variables in any scientific study on the efficacy of intercessory prayer. Curiously, no study has so far addressed these issues. And, for several reasons, such issues are disturbing because they reduce the concept of God to that of a human being with weaknesses and vanities, thereby exposing theological inconsistencies and attacking the very roots of theology and natural justice. Some of the unsettling questions that arise in these contexts are presented below; the questions are unsettling because they invite comparison with human parallels that devalue the concept of God, something that those who pray surely would not have considered. Researchers raised these important questions (6):

1. If the number, duration and frequency of prayer are important or if the number of persons praying is important, does God, like a businessman, market boons based on the currency value of the prayers? Or, will God pay attention only if those who pray are sufficiently bothersome?
2. If the type of prayer is important, is God a bureaucrat who is more likely to consider petitions that appear in the prescribed forms?
3. If the addition of vows and sacrifices is important, is God somebody who can be flattered or bribed into granting a boon?
4. If the level of fervency or intensity is important, does God distinguish between “please”, “pretty please” and “pretty please with ribbons on it”?
5. If the practical content of and petitions in the prayer are important, how does God make decisions about what is and what is not a reasonable request?
6. If the faith or conviction of the persons who pray is important, does God value the beliefs of the petitioners more than the merits of the petitions?
7. If the personal characteristics and qualities of the persons who pray (or the persons who are being prayed for) are important, are some people more equal before God than other people? Religions portray God as being compassionate; what sort of compassion is displayed by the selective favoring of an experimental over a control group?
8. If the entity to which the prayer is directed is important, do different Gods have different portfolios? Are some Gods more approachable? Do some Gods ignore some prayers? If the religious affiliation of the person who prays is important, what becomes of the other religions of the world and those who follow such religions; will their prayers remain unanswered?
9. If the magnitude of response to the petitions is total, then all prayers should result in miraculous or near-miraculous benefits. This, clearly, almost never happens. Thus, does God work on percentages; that is, if the petition is for an elephant, does he sanction a mouse? Or, are his responses only subtle ones? If so, how does he choose on the outcome measure to improve?

These questions are unsettling to those who pray because of their theological implications, but they are also unsettling to scientists because they challenge the design, analysis and interpretation of randomized controlled trials of the efficacy of intercessory prayer. Consider the following:

1. It could be difficult, if not impossible, to measure all the independent and confounding variables that are important in such research. For example, how might one measure faith, fervency, reasonableness, worthiness, religiosity, morality and other abstract constructs?
2. How might one define what is an acceptable response to prayer? Healing can be partial or complete. It can be psychological or physical. It can be abstract or concrete. Confounding the picture, statistically significant improvement can be identified only if the same outcome measure is improved in a sufficiently large number of experimental relative to control patients, but why should God decide to select any one outcome measure over the rest? And if different outcome measures improve in different experimental patients in response to prayer, there is no way in which the improvement can be statistically detected.
3. As atheists, in general, form a minority in most populations, in any randomized controlled trial of intercessory prayer, there is likely to be a number of persons (friends, relatives and the patients themselves) praying for members of both experimental and control groups, unknown to the researchers. If prayer works, this unmeasured source of healing could diminish intergroup differences in outcomes.
4. As inferential statistical tests will be applied to the data generated by randomized controlled trials of intercessory prayer, is it valid to assume that acts of God conform to normal, t or other statistical distributions? Or that God responds mechanistically to prayer, in a manner that follows laws of probability? In this context, miraculous healings are considered to be outside the provisions of nature, and so divine intervention could actually be expected to violate probability.
5. Alternately, if prayer is a nonlinear variable, the merits and demerits of which are decided upon by God, then one prayer made by a control patient or relative can statistically offset a multitude of intercessory prayers offered on behalf of the experimental patients. In fact, if divine intervention is selective or arbitrary in response to petitions, the entire basis of randomized controlled design and inferential statistical analysis becomes invalid.

From a scientific perspective, if prayer is indeed considered to work, thought should also be given to the possibility that it may not require a deity. It may, instead, invoke some hitherto unidentified mental energy that has healing power. If so, might prayer be more effective if those who pray are in closer proximity to those who are being prayed for? Might the direction in which persons face (while praying) matter? Might the assistance of the physical sciences be required to identify the nature of the biological energies at work?

It should be noted that the distant healing, intercessory prayer studies specifically test the intervention of a divine entity. This is because the intercessors are usually blind to the identities of the patients for whom they pray, or (at least) because the intercessors do not have any contact with these patients. Therefore, it is left to a sentient being to miraculously divine the intent of the prayers and apply the intercession to the correct target.

Of note, distant healing, intercessory prayer studies address soft diagnoses with soft outcomes. No study, for example, has examined whether prayer can result in the disappearance of medically proven tumors and metastases, reversal of traumatic paraplegia or revival from a state of brain death. It would seem that the results of such studies could be more convincing than the results of studies on wound healing or successful pregnancy. Could it be that those who pray believe that God has or sets limitations?

Researchers  close the critique with two final questions (6):

1. If research on intercessory prayer is positive, does it suggest to us ways and means by which we can manipulate God or make his behaviour statistically predictable?
2. Why would any divine entity be willing to submit to experiments that attempt to validate his existence and constrain his responses?

In this context, we must keep in mind that religion is based on faith and not on proof. This implies that, if God exists, he is indifferent to humanity or has chosen to obscure his presence. Either way, he would be unlikely to cooperate in scientific studies that seek to test his existence.

Where does this leave us? God may indeed exist and prayer may indeed heal like theists think and say that their research has validated this; however, it appears that, for important theological and scientific reasons, randomized controlled studies cannot be applied to the study of the efficacy of prayer in healing. In fact, no form of scientific enquiry presently available can suitably address the subject. Therefore, the continuance of such research may result in the conducted studies finding place among other seemingly impeccable studies with seemingly absurd claims (Renckens et al. 2002; [7]). Whereas some scientists have attempted to be scientifically and politically correct in their critique, other authors, such as Dawkins,[8] have been humorous, no even scathing, in their criticism.

The aim of science is not only to open a door to infinite wisdom but to set a limit to infinite error.

So  some say prayers have some effects but that is highly questionable.

Okay, coming to  the main question, If you send wishes to a dead person, he cannot have a psychological boost like living persons.  But what your wish says is how much you care about the person, how you remembered an important date in that person's life and how you still feel about that person. The dead person's close relatives and friends  might feel happy about this. This also shows how much the dead person is still loved, respected or revered. This is an important Hallmark of that person.

So you can wish the dead person to pay your respects and make all his or her loved ones happy. 

Those who are living and say these wishes mean a lot to them are denoting that they are unable to overcome their emotional dependence on them and do need them for a psychological boost. 

Coming to the emotional boost of wishes or blessings or prayers, those who have risen above the emotional aspects in their lives don't need these external boosters. I certainly don't need them and wrote a poem too on this sometime back (9).

But the irony is people who give spiritual renderings too depend on them for their emotional well being. They say you can learn how to control your emotions by rising above them to the degree of consciousness of your Higher Self (10).

When you identify with an emotion you become that emotion, even if temporarily, and then that emotion is in control as it colours all your thoughts and actions. In contrast, by learning how to control your emotions by rising above them and observing your experiences as if from above, then any associated emotions can be tempered.

This is not the same as not having or suppressing your emotions. Controlling your emotions is about changing the way you handle those experiences that trigger extreme emotional reactions within you. By observing your emotions from a higher vantage point, as if observing yourself having those emotions from a distance, you no longer identify with them.

It's not what happens to you that counts but rather how you perceive that experience, or in other words, the meaning you give to it. Any experience is in itself neutral but your emotions surrounding the experience determine its impact on you, and your emotions are in turn coloured by the core beliefs of your personal belief system. 

I am not into spiritual things but when science tells me there is no meaning to wishes, blessings or prayers in reality and that they won't affect the result or outcome in any way - I don't feel anything at all whether people wish me or not! If they find time to wish me, it is okay and I thank them for taking time to do that. If they have more  important work to do and are unable to wish for me, I can understand that and still this is also okay with me. 

It doesn't make any difference to me, dead or alive, whether people wish me or not! If people call that emotional maturity like my friends and colleagues do, that is what science has brought into my life and I thank SCIENCE for that.