Happiness can be defined as the prevalence of the frequency generated by positive emotional experiences over negative ones. The quality of life can be subdivided in two dimensions: objective well-being, which consists of the practical circumstances of live, such as income, education, health, leisure and others; and subjective well-being, which stems from our subjective experiences in life and are linked to the assessment people make of their lives, considering factors like satisfaction, mood and positive affection.
Some years ago in the Asian nation of Bhutan was created an alternative index to measure happiness. Instead of the Gross Domestic Product (GDP) index, which measured wealth, they created the Gross National Happiness (GNH) index. When a country sells its natural resources, the traditional assessment is one of growth. GNH takes into account, however, other factors, such as the environmental and social impact that can be irreversible. The GNH index calculation includes life expectancy, good education, environmental aspects and psychological well-being. 
The Brazilian psychiatrist Leonardo Machado (photo), who has a master degree and PhD in neuropsychiatry and is a member of the Medical Spiritist Association in the state of Pernambuco, gave a lecture recently entitled Happiness, a scientific and spiritual vision, as he explains in the following interview. 
What is the definition of happiness patients seek when they get to a doctor's practice or a hospital?
The vast majority of patients come to us with the idea that curing an illness or dealing with some of its symptoms will make them automatically fell good. And that is not true at all. The absence of illness or symptoms doesn't amount to the presence of positive emotions. That is what modern neuroscience and positive psychology studies have shown. 
We know that a state of unhappiness leads people to depression in some cases. Is it possible to treat people without focusing on the disease, attempting instead to improve its well-being?
That's exactly what research and studies have shown. There is a large amount of evidence, and at least two of them with the help of positive psychology, showing that it's possible to improve subjective well-being and reduce symptoms of depression and anxiety at the same time. Another meta-analysis showed positive results in attempts to increase the level of psychological well-being. So what has been shown is that it is also important to stimulate positive emotions if you want to reduce pain and anguish in a quick manner and reduce the symptoms. That has a tampon effect on the negative emotions and also helps reduce relapse. 
Happiness is subjective. How can we establish a scientific concept for it?
In the construction of science, we have followed a different path to that of the philosophers. The philosophers, and especially the Hellenics, aimed at achieving happiness in life. The cynics then said that to achieve that we would need to abolish desire. We wouldn't own anything and we wouldn't wish to have anything, as desire or ownership would by themselves generate unhappiness. That proposal is valid and is accepted by many people seeking to find happiness. But it may not be enough for other people, as happiness is indeed a subjective concept. So, instead of studying what would happiness be from a hegemonic perspective, we study the people who say they are happy. That is why a fundamental concept, built in positive psychology, is called subjective well-being. In other words, what makes this or that person's life happy. Based on his or her perception, you will see what the consequences are.
How should we look for spiritual happiness?
From a spiritual perspective, we must establish a link with the Teachings we embrace: Spiritism. That is well explained in the Spirits' Book when Allan Kardec asks whether it would be possible to find some sort of happiness on earth. The benefactors answered that yes, that common happiness would be based on owning what is essential for material life, on a clear conscience and faith in the future. These are the basic elements common to us all. They lie above religious beliefs or even the fact that the person has a religion or not.