I would argue that much of those issues, are the consequences of Residential Schools that were present in Canada and the U.S.A from the 18th century to as late as 1996 and many more societal problems common today in Native American communities.
The purpose of these schools was to assimilate natives into European culture through constant immersion. That was accomplished through removing children from their homes and enrolling them in these schools at a young age. There was little to no tolerance for the speaking of languages other than those allowed and, very often, any remotely cultural behavior or sentiments shown by these children were punishable. From alumni testimonies that have come to light, the schools were rampant with physical, psychological, emotional and sexual abuses. The institutions are cited as a major force in the cultural genocide of First Nation peoples and the experiences there as one of the leading causes for the development of depression and other mental illnesses in Native peoples in the past.
So to answer your question, the issues today are the accumulative product of several generations of colonialism and systematic oppression in North America. Much work remains to heal the damage. You can read up in more detail about government settlements, testimonies, history, and what work is being done with these sources:
Residential School Settlements, Canada
Additional question: is there any correlation here with Native Americans' increased susceptibility to alcoholism?
There actually are long cultural traditions of altruistic suicide in both Arctic and Siberian groups. If you're not up on your Durkheimian categories of suicide, "altruistic" refers to suicides intended to benefit the larger society or group. So a soldier who throws himself on a grenade is an altruistic suicide, for example. In Arctic societies and elsewhere, this typically manifests as suicide by the elderly once they begin to require substantial care. The stereotypical "old man left on an ice floe" idea is the gross simplification of this, but these incidents can also involve what could be called assisted suicides, with some blurring into what could also be termed voluntary homicide. If you have HRAF access, there are some very moving accounts of the elderly essentially badgering their children into stabbing them in the heart.
I've written about this particular phenomenon before on /r/AskHistorians. I will add this small piece from Boas' 1888 report, The Central Eskimo:
I may add here that suicide is not of rare occurrence, as according to the religious ideas of the Eskimo the souls of those who die by violence go to Qudlivun, the happy land. For the same reason it is considered lawful for a man to kill his aged parents. In suicide death is generally brought about by hanging.
So there is absolutely a tradition of altruistic elderly suicide among Arctic peoples, but this is also absolutely a red herring in discussing this question. It is a fallacy to think that the incredibly high rates of suicidality among native groups can be attributed to deeper cultural structures when the evidence is abundant that contemporary lived experiences are more explanatory. Kral (2012) says that "In order to understand suicide [among Canadian Inuit], one needs to first understand the perturbation behind it," noting that coerced settlement and acculturation in the 1950s and 60s essentially created an inter-generational disconnect. This in turn undermined the social order and methods of conflict resolution and support. As Kral puts it, "colonialism unravels the social worlds of the colonized, creating a collective anomie."
So even if the emic explanation of suicide in these societies hinges upon proximal triggering events, we cannot avoid the reality that these events are occurring against a backdrop wherein the traditional social framework has been up-ended. We can see a similar pattern in suicides in Chuuk/Truk (Hezel 1984) and in Amazonia among the Jivaroa (Brown 1986). While noting that the immediate explanation for a youth's suicide is most often social conflict in the form of romantic or familial distress, Brown notes that "the precipitating event may have only been the most conspicuous part of a longer process of deteriorating social ties." In addition to the unraveling of societal bonds, MacDonald (2003) proposes that, particular in small communities, there can be a "wave" effect of suicides as a singular event such as an economic or health crisis which triggers suicides leads to a normalization of the act, which itself leads to further suicides beyond the original epidemic.
So, again, it is misleading to think of there being a historical "tradition" of suicidality among these groups, and that being an explanation for high rates in the present. These are groups which have undergone profound and often involuntary transitions even in recent generations, so the idea of harkening back to centuries long gone as explaining the contemporary situation is intrinsically problematic even as it highlights the difficulties facing modern communities. Far more explanatory are high rates of poverty, lack of opportunities, social disconnection, prevalence of drug/alcohol abuse, and access to firearms. Patel & Kleinman (2003) did a meta-analysis on mental disorders (including suicidality) in developing countries finding that major factors to consider were income, insecurity, hopelessness, social change, education, gender, and comorbidities. While this factors certainly have historical causes, turning towards a histori-cultural explanation of high suicide rates in Native American/First Nation communities elides over the fact of present day hardships and intrinsically leads to an "othering" of those groups.
There are a host of interrelated issues that have been put forward as root causes. While the legislation and the history varies between the former colonies (US, Can, NZ, Au) here are some of them:
To make a very long story short, colonization (residential schools, reserves, epidemics, land loss, subsidence resource loss, etc.) led to loss of culture and language, breaking of family relations and social ethos over the course of generations which is today experienced as unresolved grief and PTSD which in turn lead to psychosocial issues and thus self-medication through substance abuse. While these may be viewed as individual issues they are arguably societal/collective responses to sustained oppression and ongoing systemic injustice. The state usually makes historical argument that injustice was in the past (eg. apology for residential schools in Can.) thus shifts responsibility for restitution in the present while at the same time uses contemporary Indigenous suffering to maintain state control (i.e. Indigenous people are not well enough to take care of themselves thus the state will do it for them). And the cycle repeats through weak and ineffective policy (eg. In Can the Indian Act from 1876 is still in force today, that is 139 years and counting).
Apologies that most of these are from Canada (most familiar with this literature) and not specifically about Alaskan Natives but it gives a good idea of the main arguments out there.