The present study aimed to assess trends in hospital admissions for depression, considered as a proxy for depression severity, and to relate these trends with antidepressant prescription and suicide rates in the region of Veneto between 2000 and 2005. Additionally, suicide rates were analysed in order to assess a possible link between antidepressant use and suicide. Essentially, we found a marked decline in admissions for depression, with no major change in psychiatric bed availability, an exponential increase in antidepressant prescribing, and no change in suicide rates. Also, the results show that the trend of suicide rates does not correlate with the changes in admission rates for depression. It also appears that the increase in AD prescribing does not correlate with changes in suicide rates. It may be possible that the relationship between AD prescribing and suicide rates may work only for some age strata. Older people use antidepressants far more than younger people. This finding has been confirmed for the whole of Italy . Unfortunately, we have no information on suicide rates divided by age. It appears that antidepressants are very effective in preventing suicide among older people . We also have no data on the proportion of SSRIs that make up the total number of ADs prescribed. However, we can say that it is likely that the majority of antidepressants prescribed in Veneto are SSRIs and newer ADs. The study by Guaiana and colleagues  showed that SSRIs and newer ADs had an exponential increase in prescription, whilst the prescription of older tricyclic ADs did not change. Also, two other recent studies performed in different Italian regions [23, 24] showed that the prevalence of SSRI use had markedly increased. The first and most striking finding is the sharp decline of hospital admissions for depression. This decrease affected both the age strata 16-64 and 65+ age band, as well males and females. The data relating to the 0-14 age strata are not reliable due to the small numbers involved. This finding is at odds with that of Vyssoki and colleagues , who found that an increase in hospital admissions for depression was in parallel with a decrease in suicide rates. There are several possible explanations to the findings in the 16-64 and 65+ age bands. In theory, fewer hospital admissions may just reflect a decrease in the general prevalence of depression, or a decrease in recognition of depression, or both. There is no evidence to suggest either. On the contrary, worldwide data have repeatedly documented an increase in the incidence and/or awareness of depression both amongst the general population and medical practitioners . Moreover, both trends would be at odds with our second finding of an impressive increase in antidepressant prescription in the same region at the same time. Another possibility is that the observed decrease in hospital admission merely reflects a decrease in bed availability. This however does not seem to be the case as the number of beds did not decline. The most likely explanation of the observed decline in hospital admissions for depression between 2000 and 2005 is that depression became better diagnosed, and therefore better treated. This notion becomes particularly salient when considering our next finding of an approximately fivefold increase in antidepressant use in the same period. It is most plausible that the observed increase in antidepressant prescribing reflects a better effort in recognising depression, and therefore earlier and more effective treatment. The benefits of early intervention have been widely documented , resulting in the shortening of the depressive episode. If, as mentioned above, hospital admissions are a valid indicator of depression severity [10, 11], then it is arguable that the decrease in hospital admissions is directly linked to an increase in effective prescription of antidepressants. It is of note that a worldwide increase in the prescription of antidepressants has been observed over the last 10-15 years .
There have been some reports showing that admissions for depression increased or did not change [2, 14, 15]. Shajahan  reported that admissions increased in males in Scotland. They hypothesised that this may be due to increased recognition of depression or an increase in the health-seeking behaviour of males. The study by Shajahan refers to an earlier timeframe (1980-1995). It is possible to hypothesise that since the late 1990s, there has been an increased awareness of depression, possibly leading to an increase in the number of the people treated with antidepressants, which eventually led to an overall decrease in depression severity and therefore in admissions for depression. The increased awareness for depression may likely have happened in primary care scenarios. It appears that general practitioners prescribe more and more ADs in some European regions . To corroborate this hypothesis, Munoz-Arroyo and colleagues  found that prescription of antidepressants by general practitioners doubled in Scotland from 1992 to 2000. Also, the studies by Walsh  and Guaiana et al. , examining admissions in Ireland and in Italy, respectively, referred to an earlier timeframe. Our hypothesis is that there has been a time lag between increased prescription of antidepressants and reductions in admissions for depression. In Italy, antidepressant prescribing has increased exponentially only since 1995 . We hypothesise that it may have taken some years to see an effect on depression and admissions for depression.
Also, it is of interest to note that the decrease in admissions for depression is not associated with change in suicide rate, as we found no correlation between admissions for depression and suicide rates, for both sexes. Our final finding is that overall suicide rates remained unchanged during the period under examination, in spite of the observed exponential increase in use of antidepressants. If antidepressants were associated with an increase in suicide rates, as pointed out by Healy and colleagues , there would have been an increase in suicide rates, which did not happen. Vichi and colleagues examined suicide rates in Italy between 1980 and 2002 . They concluded that the decline in suicide rates was possibly a consequence of the decrease in the incidence of mental disorders as a result of the development of an integrated and community-based mental health system, which in turn may have led to decreased suicide rates as a consequence of early detection of mental disorders, including depression. AD prescribing may be part of this picture, as earlier detection of mental disorders may have led to an increase in AD prescribing. Our findings are more in line with the data examined by Isaacson and colleagues [5, 6], and Barbui and colleagues  where suicide rates showed an opposite trend to antidepressant prescribing. Also, Khan and colleagues  showed that SSRIs do not induce suicide more than other ADs or even placebo. Regardless, our study failed to find any argument suggesting that an increase in antidepressant use is associated with increased risk of suicide.
The present study suffers from some limitations, however. First we assumed that all antidepressants are prescribed and used for depression. This is not entirely true, as antidepressants are increasingly used for anxiety disorders as well, and this is the case in Italy . Anxiety disorders are at least as prevalent as depression. Both types of disorders are highly comorbid. Our database does not make it possible to find out the specific disease that required the prescription of the antidepressant. However, since anxiety and depression are closely intermingled, the former often being an indicator of the severity of the latter and vice versa , this limitation does not necessarily invalidate our main conclusions. Secondly, data on antidepressant prescribing does not cover the entire Veneto region, but only some of the LHUs. We have assumed that the data can be extended to the whole region but we cannot rule out a possible bias in data collection. Also, the study covers a relatively limited period of time; only 6 years. Nevertheless, clear trends can be seen. Thirdly, we cannot exclude the possibility that that the downward trend in hospital admissions for depression in Veneto and in Italy could be part of a broader picture, where admissions for mental health problems as a whole are decreasing. Moreover, the DDD only reflects prescription and not current usage. It is not possible to take for granted that all people who receive a prescription will use it. It must also be said that the reliability of data on admissions, suicides and DDD may be questioned, as happens for any large-scale data collection. Another point to consider is that suicide is not only linked to depression but also to schizophrenia, bipolar disorder and substance misuse [31–33]. Our data do not include admissions for those conditions. Findings may have been different if we had included admissions for those mental disorders. Finally, the naturalistic design of this analysis is by definition subject to ecological fallacy, and therefore no causal relationships can be definitely established.