I won't repeat what you can already Google. There is a lot of research out there, some well designed and executed. None of the research has shown any adverse effects from meditation. All research has focused on measuring physical or emotional stimuli.
One cannot directly measure spirituality and this is the limitation of any research. One should remember that the goal of meditation is to proactively connect with our inner self or source. Any other results are in fact side benefits, although they are important.
The obvious side benefits are lowered negative stress levels (which leads to a healthier body and mental frame), reduced blood pressure and increase in creativity and attention span. These are the most common findings of research.
Just as a trained adept can fool a lie detector, exhibiting some or all of the above mentioned "side effects" is not proof that someone is spiritually advanced.
Finally, one should bear in mind that with the massively increased reach of social networks and the internet, small signals or findings get more attention than deserved. Thus a minor, possibly incorrect, result is repeated or "liked" often enough that it starts to look like a major result. In other words, one has to use ones common sense when interpreting.
Based on my own experience and that of other meditators I have observed over the last few decades, here's my list of some benefits that research has not hi-lighted yet. These benefits are in proportion to the depth and frequency of ones practice.
Improved strength and fortitude in the face of adversity
Increased sense and prevalence of quietness and calmness
Fearlessness and less worrying
Breaking away from destructive habits e.g. smoking
We live in a physical body and we are an intimate part of our loved ones and society. Death, disease, making mistakes (often many times over) and pain are a part of living as is learning to forgive and depend on each other. Such events and especially the fear of such events cause us to behave in fearful ways. Fear of losing ones job can cause one to behave negatively towards other colleagues. Losing a job can cause one to go into a negative spiral of low self-esteem. Similary finding the next job, pushes ones emotions to the other end of the scale. In this way we swing from one emotion to another. We are prisoners of our feelings and we always try to maximise the positive ones.
This continual jostling, like a rudderless boat on a rough sea, from one emotional state to another, is what drains us of our energies and balance.
The more we practice meditation, the more we consciously connect wth our one true source. This in turn results in us being less fearful of losing control. This is why research shows that those who meditate, experience lower negative stress levels and more of the associated benefits.
The improved ability to withstand pain, stress, loss; the increased tendency to drop harmful habits and bad behaviours and the high prevalence of calmness and inner sense of quietness are a direct result of experiencing deeper and persistent connections with your inner self.
The meditator will still experience pain and loss, but it will be tempered with wisdom and spiritual insight in proporation to the level of spiritual realization achieved.
Balance and "earned wisdom" create a restful, calm energy with an "effortless focus".
Creativity is the ability to spontaneously and intuitively generate ideas and connections from the sum of our experience and knowledge. Creativity is at its best and most natural when the mind is still. At any given moment, our minds are operating at conscious and subconscious, at emotional and logical levels. The more busy we are mentally, the less space we give over to being intuitively creative.
Deep meditation stills the mind allowing the creative process to function again.
Last update: v2014 09 30 2.01